add BPM detection

daw-backend/src/audio/bpm_detector.rs

@@ -0,0 +1,310 @@
+/// BPM Detection using autocorrelation and onset detection
+///
+/// This module provides both offline analysis (for audio import)
+/// and real-time streaming analysis (for the BPM detector node)
+
+use std::collections::VecDeque;
+
+/// Detects BPM from a complete audio buffer (offline analysis)
+pub fn detect_bpm_offline(audio: &[f32], sample_rate: u32) -> Option<f32> {
+    if audio.is_empty() {
+        return None;
+    }
+
+    // Convert to mono if needed (already mono in our case)
+    // Downsample for efficiency (analyze every 4th sample for faster processing)
+    let downsampled: Vec<f32> = audio.iter().step_by(4).copied().collect();
+    let effective_sample_rate = sample_rate / 4;
+
+    // Detect onsets using energy-based method
+    let onsets = detect_onsets(&downsampled, effective_sample_rate);
+
+    if onsets.len() < 4 {
+        return None;
+    }
+
+    // Calculate onset strength function for autocorrelation
+    let onset_envelope = calculate_onset_envelope(&onsets, downsampled.len(), effective_sample_rate);
+
+    // Further downsample onset envelope for BPM analysis
+    // For 60-200 BPM (1-3.33 Hz), we only need ~10 Hz sample rate by Nyquist
+    // Use 100 Hz for good margin (100 samples per second)
+    let tempo_sample_rate = 100.0;
+    let downsample_factor = (effective_sample_rate as f32 / tempo_sample_rate) as usize;
+    let downsampled_envelope: Vec<f32> = onset_envelope
+        .iter()
+        .step_by(downsample_factor.max(1))
+        .copied()
+        .collect();
+
+    // Use autocorrelation to find the fundamental period
+    let bpm = detect_bpm_autocorrelation(&downsampled_envelope, tempo_sample_rate as u32);
+
+    bpm
+}
+
+/// Calculate an onset envelope from detected onsets
+fn calculate_onset_envelope(onsets: &[usize], total_length: usize, sample_rate: u32) -> Vec<f32> {
+    // Create a sparse representation of onsets with exponential decay
+    let mut envelope = vec![0.0; total_length];
+    let decay_samples = (sample_rate as f32 * 0.05) as usize; // 50ms decay
+
+    for &onset in onsets {
+        if onset < total_length {
+            envelope[onset] = 1.0;
+            // Add exponential decay after onset
+            for i in 1..decay_samples.min(total_length - onset) {
+                let decay_value = (-3.0 * i as f32 / decay_samples as f32).exp();
+                envelope[onset + i] = f32::max(envelope[onset + i], decay_value);
+            }
+        }
+    }
+
+    envelope
+}
+
+/// Detect BPM using autocorrelation on onset envelope
+fn detect_bpm_autocorrelation(onset_envelope: &[f32], sample_rate: u32) -> Option<f32> {
+    // BPM range: 60-200 BPM
+    let min_bpm = 60.0;
+    let max_bpm = 200.0;
+
+    let min_lag = (60.0 * sample_rate as f32 / max_bpm) as usize;
+    let max_lag = (60.0 * sample_rate as f32 / min_bpm) as usize;
+
+    if max_lag >= onset_envelope.len() / 2 {
+        return None;
+    }
+
+    // Calculate autocorrelation for tempo range
+    let mut best_lag = min_lag;
+    let mut best_correlation = 0.0;
+
+    for lag in min_lag..=max_lag {
+        let mut correlation = 0.0;
+        let mut count = 0;
+
+        for i in 0..(onset_envelope.len() - lag) {
+            correlation += onset_envelope[i] * onset_envelope[i + lag];
+            count += 1;
+        }
+
+        if count > 0 {
+            correlation /= count as f32;
+
+            // Bias toward faster tempos slightly (common in EDM)
+            let bias = 1.0 + (lag as f32 - min_lag as f32) / (max_lag - min_lag) as f32 * 0.1;
+            correlation /= bias;
+
+            if correlation > best_correlation {
+                best_correlation = correlation;
+                best_lag = lag;
+            }
+        }
+    }
+
+    // Convert best lag to BPM
+    let bpm = 60.0 * sample_rate as f32 / best_lag as f32;
+
+    // Check for octave errors by testing multiples
+    // Common ranges: 60-90 (slow), 90-140 (medium), 140-200 (fast)
+    let half_bpm = bpm / 2.0;
+    let double_bpm = bpm * 2.0;
+    let quad_bpm = bpm * 4.0;
+
+    // Choose the octave that falls in the most common range (100-180 BPM for EDM/pop)
+    let final_bpm = if quad_bpm >= 100.0 && quad_bpm <= 200.0 {
+        // Very slow detection, multiply by 4
+        quad_bpm
+    } else if double_bpm >= 100.0 && double_bpm <= 200.0 {
+        // Slow detection, multiply by 2
+        double_bpm
+    } else if bpm >= 100.0 && bpm <= 200.0 {
+        // Already in good range
+        bpm
+    } else if half_bpm >= 100.0 && half_bpm <= 200.0 {
+        // Too fast detection, divide by 2
+        half_bpm
+    } else {
+        // Outside ideal range, use as-is
+        bpm
+    };
+
+    // Round to nearest 0.5 BPM for cleaner values
+    Some((final_bpm * 2.0).round() / 2.0)
+}
+
+/// Detect onsets (beat events) in audio using energy-based method
+fn detect_onsets(audio: &[f32], sample_rate: u32) -> Vec<usize> {
+    let mut onsets = Vec::new();
+
+    // Window size for energy calculation (~20ms)
+    let window_size = ((sample_rate as f32 * 0.02) as usize).max(1);
+    let hop_size = window_size / 2;
+
+    if audio.len() < window_size {
+        return onsets;
+    }
+
+    // Calculate energy for each window
+    let mut energies = Vec::new();
+    let mut pos = 0;
+    while pos + window_size <= audio.len() {
+        let window = &audio[pos..pos + window_size];
+        let energy: f32 = window.iter().map(|&s| s * s).sum();
+        energies.push(energy / window_size as f32); // Normalize
+        pos += hop_size;
+    }
+
+    if energies.len() < 3 {
+        return onsets;
+    }
+
+    // Calculate energy differences (onset strength)
+    let mut onset_strengths = Vec::new();
+    for i in 1..energies.len() {
+        let diff = (energies[i] - energies[i - 1]).max(0.0); // Only positive changes
+        onset_strengths.push(diff);
+    }
+
+    // Find threshold (adaptive)
+    let mean_strength: f32 = onset_strengths.iter().sum::<f32>() / onset_strengths.len() as f32;
+    let threshold = mean_strength * 1.5; // 1.5x mean
+
+    // Peak picking with minimum distance
+    let min_distance = sample_rate as usize / 10; // Minimum 100ms between onsets
+    let mut last_onset = 0;
+
+    for (i, &strength) in onset_strengths.iter().enumerate() {
+        if strength > threshold {
+            let sample_pos = (i + 1) * hop_size;
+
+            // Check if it's a local maximum and far enough from last onset
+            let is_local_max = (i == 0 || onset_strengths[i - 1] <= strength) &&
+                              (i == onset_strengths.len() - 1 || onset_strengths[i + 1] < strength);
+
+            if is_local_max && (onsets.is_empty() || sample_pos - last_onset >= min_distance) {
+                onsets.push(sample_pos);
+                last_onset = sample_pos;
+            }
+        }
+    }
+
+    onsets
+}
+
+/// Real-time BPM detector for streaming audio
+pub struct BpmDetectorRealtime {
+    sample_rate: u32,
+
+    // Circular buffer for recent audio (e.g., 10 seconds)
+    audio_buffer: VecDeque<f32>,
+    max_buffer_samples: usize,
+
+    // Current BPM estimate
+    current_bpm: f32,
+
+    // Update interval (samples)
+    samples_since_update: usize,
+    update_interval: usize,
+
+    // Smoothing
+    bpm_history: VecDeque<f32>,
+    history_size: usize,
+}
+
+impl BpmDetectorRealtime {
+    pub fn new(sample_rate: u32, buffer_duration_seconds: f32) -> Self {
+        let max_buffer_samples = (sample_rate as f32 * buffer_duration_seconds) as usize;
+        let update_interval = sample_rate as usize; // Update every 1 second
+
+        Self {
+            sample_rate,
+            audio_buffer: VecDeque::with_capacity(max_buffer_samples),
+            max_buffer_samples,
+            current_bpm: 120.0, // Default BPM
+            samples_since_update: 0,
+            update_interval,
+            bpm_history: VecDeque::with_capacity(8),
+            history_size: 8,
+        }
+    }
+
+    /// Process a chunk of audio and return current BPM estimate
+    pub fn process(&mut self, audio: &[f32]) -> f32 {
+        // Add samples to buffer
+        for &sample in audio {
+            if self.audio_buffer.len() >= self.max_buffer_samples {
+                self.audio_buffer.pop_front();
+            }
+            self.audio_buffer.push_back(sample);
+        }
+
+        self.samples_since_update += audio.len();
+
+        // Periodically re-analyze
+        if self.samples_since_update >= self.update_interval && self.audio_buffer.len() > self.sample_rate as usize {
+            self.samples_since_update = 0;
+
+            // Convert buffer to slice for analysis
+            let buffer_vec: Vec<f32> = self.audio_buffer.iter().copied().collect();
+
+            if let Some(detected_bpm) = detect_bpm_offline(&buffer_vec, self.sample_rate) {
+                // Add to history for smoothing
+                if self.bpm_history.len() >= self.history_size {
+                    self.bpm_history.pop_front();
+                }
+                self.bpm_history.push_back(detected_bpm);
+
+                // Use median of recent detections for stability
+                let mut sorted_history: Vec<f32> = self.bpm_history.iter().copied().collect();
+                sorted_history.sort_by(|a, b| a.partial_cmp(b).unwrap());
+                self.current_bpm = sorted_history[sorted_history.len() / 2];
+            }
+        }
+
+        self.current_bpm
+    }
+
+    pub fn get_bpm(&self) -> f32 {
+        self.current_bpm
+    }
+
+    pub fn reset(&mut self) {
+        self.audio_buffer.clear();
+        self.bpm_history.clear();
+        self.samples_since_update = 0;
+        self.current_bpm = 120.0;
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_120_bpm_detection() {
+        let sample_rate = 48000;
+        let bpm = 120.0;
+        let beat_interval = 60.0 / bpm;
+        let beat_samples = (sample_rate as f32 * beat_interval) as usize;
+
+        // Generate 8 beats
+        let mut audio = vec![0.0; beat_samples * 8];
+        for beat in 0..8 {
+            let pos = beat * beat_samples;
+            // Add a sharp transient at each beat
+            for i in 0..100 {
+                audio[pos + i] = (1.0 - i as f32 / 100.0) * 0.8;
+            }
+        }
+
+        let detected = detect_bpm_offline(&audio, sample_rate);
+        assert!(detected.is_some());
+        let detected_bpm = detected.unwrap();
+
+        // Allow 5% tolerance
+        assert!((detected_bpm - bpm).abs() / bpm < 0.05,
+                "Expected ~{} BPM, got {}", bpm, detected_bpm);
+    }
+}

daw-backend/src/audio/engine.rs

@@ -68,7 +68,7 @@ impl Engine {
         let buffer_size = 512 * channels as usize;
 
         Self {
-            project: Project::new(),
+            project: Project::new(sample_rate),
             audio_pool: AudioPool::new(),
             buffer_pool: BufferPool::new(8, buffer_size), // 8 buffers should handle deep nesting
             playhead: 0,
@@ -637,7 +637,7 @@ impl Engine {
                 self.recording_state = None;
 
                 // Clear all project data
-                self.project = Project::new();
+                self.project = Project::new(self.sample_rate);
 
                 // Clear audio pool
                 self.audio_pool = AudioPool::new();
@@ -726,6 +726,7 @@ impl Engine {
                             "Chorus" => Box::new(ChorusNode::new("Chorus".to_string())),
                             "Compressor" => Box::new(CompressorNode::new("Compressor".to_string())),
                             "Constant" => Box::new(ConstantNode::new("Constant".to_string())),
+                            "BpmDetector" => Box::new(BpmDetectorNode::new("BPM Detector".to_string())),
                             "EnvelopeFollower" => Box::new(EnvelopeFollowerNode::new("Envelope Follower".to_string())),
                             "Limiter" => Box::new(LimiterNode::new("Limiter".to_string())),
                             "Math" => Box::new(MathNode::new("Math".to_string())),
@@ -810,6 +811,7 @@ impl Engine {
                             "Chorus" => Box::new(ChorusNode::new("Chorus".to_string())),
                             "Compressor" => Box::new(CompressorNode::new("Compressor".to_string())),
                             "Constant" => Box::new(ConstantNode::new("Constant".to_string())),
+                            "BpmDetector" => Box::new(BpmDetectorNode::new("BPM Detector".to_string())),
                             "EnvelopeFollower" => Box::new(EnvelopeFollowerNode::new("Envelope Follower".to_string())),
                             "Limiter" => Box::new(LimiterNode::new("Limiter".to_string())),
                             "Math" => Box::new(MathNode::new("Math".to_string())),
@@ -1668,6 +1670,7 @@ pub struct EngineController {
     playhead: Arc<AtomicU64>,
     next_midi_clip_id: Arc<AtomicU32>,
     sample_rate: u32,
+    #[allow(dead_code)] // Used in public getter method
     channels: u32,
 }
 

daw-backend/src/audio/mod.rs

@@ -1,4 +1,5 @@
 pub mod automation;
+pub mod bpm_detector;
 pub mod buffer_pool;
 pub mod clip;
 pub mod engine;

daw-backend/src/audio/node_graph/nodes/bpm_detector.rs

@@ -0,0 +1,165 @@
+use crate::audio::bpm_detector::BpmDetectorRealtime;
+use crate::audio::node_graph::{AudioNode, NodeCategory, NodePort, Parameter, ParameterUnit, SignalType};
+use crate::audio::midi::MidiEvent;
+
+const PARAM_SMOOTHING: u32 = 0;
+
+/// BPM Detector Node - analyzes audio input and outputs tempo as CV
+/// CV output represents BPM (e.g., 0.12 = 120 BPM when scaled appropriately)
+pub struct BpmDetectorNode {
+    name: String,
+    detector: BpmDetectorRealtime,
+    smoothing: f32,  // Smoothing factor for output (0-1)
+    last_output: f32, // For smooth transitions
+    sample_rate: u32, // Current sample rate
+    inputs: Vec<NodePort>,
+    outputs: Vec<NodePort>,
+    parameters: Vec<Parameter>,
+}
+
+impl BpmDetectorNode {
+    pub fn new(name: impl Into<String>) -> Self {
+        let name = name.into();
+
+        let inputs = vec![
+            NodePort::new("Audio In", SignalType::Audio, 0),
+        ];
+
+        let outputs = vec![
+            NodePort::new("BPM CV", SignalType::CV, 0),
+        ];
+
+        let parameters = vec![
+            Parameter::new(PARAM_SMOOTHING, "Smoothing", 0.0, 1.0, 0.9, ParameterUnit::Percent),
+        ];
+
+        // Use 10 second buffer for analysis
+        let detector = BpmDetectorRealtime::new(48000, 10.0);
+
+        Self {
+            name,
+            detector,
+            smoothing: 0.9,
+            last_output: 120.0,
+            sample_rate: 48000,
+            inputs,
+            outputs,
+            parameters,
+        }
+    }
+}
+
+impl AudioNode for BpmDetectorNode {
+    fn category(&self) -> NodeCategory {
+        NodeCategory::Utility
+    }
+
+    fn inputs(&self) -> &[NodePort] {
+        &self.inputs
+    }
+
+    fn outputs(&self) -> &[NodePort] {
+        &self.outputs
+    }
+
+    fn parameters(&self) -> &[Parameter] {
+        &self.parameters
+    }
+
+    fn set_parameter(&mut self, id: u32, value: f32) {
+        match id {
+            PARAM_SMOOTHING => self.smoothing = value.clamp(0.0, 1.0),
+            _ => {}
+        }
+    }
+
+    fn get_parameter(&self, id: u32) -> f32 {
+        match id {
+            PARAM_SMOOTHING => self.smoothing,
+            _ => 0.0,
+        }
+    }
+
+    fn process(
+        &mut self,
+        inputs: &[&[f32]],
+        outputs: &mut [&mut [f32]],
+        _midi_inputs: &[&[MidiEvent]],
+        _midi_outputs: &mut [&mut Vec<MidiEvent>],
+        sample_rate: u32,
+    ) {
+        // Recreate detector if sample rate changed
+        if sample_rate != self.sample_rate {
+            self.sample_rate = sample_rate;
+            self.detector = BpmDetectorRealtime::new(sample_rate, 10.0);
+        }
+
+        if outputs.is_empty() {
+            return;
+        }
+
+        let output = &mut outputs[0];
+        let length = output.len();
+
+        let input = if !inputs.is_empty() && !inputs[0].is_empty() {
+            inputs[0]
+        } else {
+            // Fill output with last known BPM
+            for i in 0..length {
+                output[i] = self.last_output / 1000.0; // Scale BPM for CV (e.g., 120 BPM -> 0.12)
+            }
+            return;
+        };
+
+        // Process audio through detector
+        let detected_bpm = self.detector.process(input);
+
+        // Apply smoothing
+        let target_bpm = detected_bpm;
+        let smoothed_bpm = self.last_output * self.smoothing + target_bpm * (1.0 - self.smoothing);
+        self.last_output = smoothed_bpm;
+
+        // Output BPM as CV (scaled down for typical CV range)
+        // BPM / 1000 gives us reasonable CV values (60-180 BPM -> 0.06-0.18)
+        let cv_value = smoothed_bpm / 1000.0;
+
+        // Fill entire output buffer with current BPM value
+        for i in 0..length {
+            output[i] = cv_value;
+        }
+    }
+
+    fn reset(&mut self) {
+        self.detector.reset();
+        self.last_output = 120.0;
+    }
+
+    fn node_type(&self) -> &str {
+        "BpmDetector"
+    }
+
+    fn name(&self) -> &str {
+        &self.name
+    }
+
+    fn clone_node(&self) -> Box<dyn AudioNode> {
+        Box::new(Self {
+            name: self.name.clone(),
+            detector: BpmDetectorRealtime::new(self.sample_rate, 10.0),
+            smoothing: self.smoothing,
+            last_output: self.last_output,
+            sample_rate: self.sample_rate,
+            inputs: self.inputs.clone(),
+            outputs: self.outputs.clone(),
+            parameters: self.parameters.clone(),
+        })
+    }
+
+    fn as_any_mut(&mut self) -> &mut dyn std::any::Any {
+        self
+    }
+
+    fn as_any(&self) -> &dyn std::any::Any {
+        self
+    }
+}

daw-backend/src/audio/node_graph/nodes/mod.rs

@@ -3,6 +3,7 @@ mod audio_input;
 mod audio_to_cv;
 mod automation_input;
 mod bit_crusher;
+mod bpm_detector;
 mod chorus;
 mod compressor;
 mod constant;
@@ -44,6 +45,7 @@ pub use audio_input::AudioInputNode;
 pub use audio_to_cv::AudioToCVNode;
 pub use automation_input::{AutomationInputNode, AutomationKeyframe, InterpolationType};
 pub use bit_crusher::BitCrusherNode;
+pub use bpm_detector::BpmDetectorNode;
 pub use chorus::ChorusNode;
 pub use compressor::CompressorNode;
 pub use constant::ConstantNode;

daw-backend/src/audio/project.rs

@@ -13,15 +13,17 @@ pub struct Project {
     tracks: HashMap<TrackId, TrackNode>,
     next_track_id: TrackId,
     root_tracks: Vec<TrackId>, // Top-level tracks (not in any group)
+    sample_rate: u32, // System sample rate
 }
 
 impl Project {
     /// Create a new empty project
-    pub fn new() -> Self {
+    pub fn new(sample_rate: u32) -> Self {
         Self {
             tracks: HashMap::new(),
             next_track_id: 0,
             root_tracks: Vec::new(),
+            sample_rate,
         }
     }
 
@@ -42,7 +44,7 @@ impl Project {
     /// The new track's ID
     pub fn add_audio_track(&mut self, name: String, parent_id: Option<TrackId>) -> TrackId {
         let id = self.next_id();
-        let track = AudioTrack::new(id, name);
+        let track = AudioTrack::new(id, name, self.sample_rate);
         self.tracks.insert(id, TrackNode::Audio(track));
 
         if let Some(parent) = parent_id {
@@ -94,7 +96,7 @@ impl Project {
     /// The new track's ID
     pub fn add_midi_track(&mut self, name: String, parent_id: Option<TrackId>) -> TrackId {
         let id = self.next_id();
-        let track = MidiTrack::new(id, name);
+        let track = MidiTrack::new(id, name, self.sample_rate);
         self.tracks.insert(id, TrackNode::Midi(track));
 
         if let Some(parent) = parent_id {
@@ -422,6 +424,6 @@ impl Project {
 
 impl Default for Project {
     fn default() -> Self {
-        Self::new()
+        Self::new(48000) // Use 48kHz as default, will be overridden when created with actual sample rate
     }
 }

daw-backend/src/audio/track.rs

@@ -303,16 +303,15 @@ pub struct MidiTrack {
 
 impl MidiTrack {
     /// Create a new MIDI track with default settings
-    pub fn new(id: TrackId, name: String) -> Self {
-        // Use default sample rate and a large buffer size that can accommodate any callback
-        let default_sample_rate = 48000;
+    pub fn new(id: TrackId, name: String, sample_rate: u32) -> Self {
+        // Use a large buffer size that can accommodate any callback
         let default_buffer_size = 8192;
 
         Self {
             id,
             name,
             clips: Vec::new(),
-            instrument_graph: AudioGraph::new(default_sample_rate, default_buffer_size),
+            instrument_graph: AudioGraph::new(sample_rate, default_buffer_size),
             volume: 1.0,
             muted: false,
             solo: false,
@@ -498,21 +497,24 @@ pub struct AudioTrack {
 
 impl AudioTrack {
     /// Create a new audio track with default settings
-    pub fn new(id: TrackId, name: String) -> Self {
-        // Use default sample rate and a large buffer size that can accommodate any callback
-        let default_sample_rate = 48000;
+    pub fn new(id: TrackId, name: String, sample_rate: u32) -> Self {
+        // Use a large buffer size that can accommodate any callback
         let default_buffer_size = 8192;
 
         // Create the effects graph with default AudioInput -> AudioOutput chain
-        let mut effects_graph = AudioGraph::new(default_sample_rate, default_buffer_size);
+        let mut effects_graph = AudioGraph::new(sample_rate, default_buffer_size);
 
         // Add AudioInput node
         let input_node = Box::new(AudioInputNode::new("Audio Input"));
         let input_id = effects_graph.add_node(input_node);
+        // Set position for AudioInput (left side, similar to instrument preset spacing)
+        effects_graph.set_node_position(input_id, 100.0, 150.0);
 
         // Add AudioOutput node
         let output_node = Box::new(AudioOutputNode::new("Audio Output"));
         let output_id = effects_graph.add_node(output_node);
+        // Set position for AudioOutput (right side, spaced apart)
+        effects_graph.set_node_position(output_id, 500.0, 150.0);
 
         // Connect AudioInput -> AudioOutput
         let _ = effects_graph.connect(input_id, 0, output_id, 0);

src-tauri/src/audio.rs

@@ -10,6 +10,7 @@ pub struct AudioFileMetadata {
     pub sample_rate: u32,
     pub channels: u32,
     pub waveform: Vec<WaveformPeak>,
+    pub detected_bpm: Option<f32>,  // Detected BPM from audio analysis
 }
 
 #[derive(serde::Serialize)]
@@ -272,6 +273,18 @@ pub async fn audio_load_file(
     let sample_rate = audio_file.sample_rate;
     let channels = audio_file.channels;
 
+    // Detect BPM from audio (mix to mono if stereo)
+    let mono_audio: Vec<f32> = if channels == 2 {
+        // Mix stereo to mono
+        audio_file.data.chunks(2)
+            .map(|chunk| (chunk[0] + chunk.get(1).unwrap_or(&0.0)) * 0.5)
+            .collect()
+    } else {
+        audio_file.data.clone()
+    };
+
+    let detected_bpm = daw_backend::audio::bpm_detector::detect_bpm_offline(&mono_audio, sample_rate);
+
     // Get a lock on the audio state and send the loaded data to the audio thread
     let mut audio_state = state.lock().unwrap();
 
@@ -293,6 +306,7 @@ pub async fn audio_load_file(
             sample_rate,
             channels,
             waveform,
+            detected_bpm,
         })
     } else {
         Err("Audio not initialized".to_string())

src/actions/index.js

@@ -536,6 +536,37 @@ export const actions = {
         if (context.timelineWidget) {
           context.timelineWidget.requestRedraw();
         }
+
+        // Make this the active track
+        if (context.activeObject) {
+          context.activeObject.activeLayer = newAudioTrack;
+          updateLayers(); // Refresh to show active state
+          // Reload node editor to show the new track's graph
+          if (context.reloadNodeEditor) {
+            await context.reloadNodeEditor();
+          }
+        }
+
+        // Prompt user to set BPM if detected
+        if (metadata.detected_bpm && context.timelineWidget) {
+          const currentBpm = context.timelineWidget.timelineState.bpm;
+          const detectedBpm = metadata.detected_bpm;
+          const shouldSetBpm = confirm(
+            `Detected BPM: ${detectedBpm}\n\n` +
+            `Current project BPM: ${currentBpm}\n\n` +
+            `Would you like to set the project BPM to ${detectedBpm}?`
+          );
+
+          if (shouldSetBpm) {
+            context.timelineWidget.timelineState.bpm = detectedBpm;
+            context.timelineWidget.requestRedraw(); // Redraw to show updated BPM
+            console.log(`Project BPM set to ${detectedBpm}`);
+            // Notify all registered listeners of BPM change
+            if (context.notifyBpmChange) {
+              context.notifyBpmChange(detectedBpm);
+            }
+          }
+        }
       } catch (error) {
         console.error('Failed to load audio:', error);
         // Update clip to show error

src/main.js

@@ -4293,6 +4293,10 @@ function timelineV2() {
           if (timelineWidget.requestRedraw) {
             timelineWidget.requestRedraw();
           }
+          // Notify all registered listeners of BPM change
+          if (context.notifyBpmChange) {
+            context.notifyBpmChange(bpm);
+          }
         }
       } else if (action === 'edit-time-signature') {
         // Clicked on time signature - show custom dropdown with common options
@@ -6681,6 +6685,84 @@ function nodeEditor() {
       set suppressActionRecording(value) { suppressActionRecording = value; }
     };
 
+    // Initialize BPM change notification system
+    // This allows nodes to register callbacks to be notified when BPM changes
+    const bpmChangeListeners = new Set();
+
+    context.registerBpmChangeListener = (callback) => {
+      bpmChangeListeners.add(callback);
+      return () => bpmChangeListeners.delete(callback); // Return unregister function
+    };
+
+    context.notifyBpmChange = (newBpm) => {
+      console.log(`BPM changed to ${newBpm}, notifying ${bpmChangeListeners.size} listeners`);
+      bpmChangeListeners.forEach(callback => {
+        try {
+          callback(newBpm);
+        } catch (error) {
+          console.error('Error in BPM change listener:', error);
+        }
+      });
+    };
+
+    // Register a listener to update all synced Phaser nodes when BPM changes
+    context.registerBpmChangeListener((newBpm) => {
+      if (!editor) return;
+
+      const module = editor.module;
+      const allNodes = editor.drawflow.drawflow[module]?.data || {};
+
+      // Beat division definitions for conversion
+      const beatDivisions = [
+        { label: '4 bars', multiplier: 16.0 },
+        { label: '2 bars', multiplier: 8.0 },
+        { label: '1 bar', multiplier: 4.0 },
+        { label: '1/2', multiplier: 2.0 },
+        { label: '1/4', multiplier: 1.0 },
+        { label: '1/8', multiplier: 0.5 },
+        { label: '1/16', multiplier: 0.25 },
+        { label: '1/32', multiplier: 0.125 },
+        { label: '1/2T', multiplier: 2.0/3.0 },
+        { label: '1/4T', multiplier: 1.0/3.0 },
+        { label: '1/8T', multiplier: 0.5/3.0 }
+      ];
+
+      // Iterate through all nodes to find synced Phaser nodes
+      for (const [nodeId, nodeData] of Object.entries(allNodes)) {
+        // Check if this is a Phaser node with sync enabled
+        if (nodeData.name === 'Phaser' && nodeData.data.backendId !== null) {
+          const nodeElement = document.getElementById(`node-${nodeId}`);
+          if (!nodeElement) continue;
+
+          const syncCheckbox = nodeElement.querySelector(`#sync-${nodeId}`);
+          if (!syncCheckbox || !syncCheckbox.checked) continue;
+
+          // Get the current rate slider value (beat division index)
+          const rateSlider = nodeElement.querySelector(`input[data-param="0"]`); // rate is param 0
+          if (!rateSlider) continue;
+
+          const beatDivisionIndex = Math.min(10, Math.max(0, Math.round(parseFloat(rateSlider.value))));
+          const beatsPerSecond = newBpm / 60.0;
+          const quarterNotesPerCycle = beatDivisions[beatDivisionIndex].multiplier;
+          const hz = beatsPerSecond / quarterNotesPerCycle;
+
+          // Update the backend parameter
+          const trackInfo = getCurrentTrack();
+          if (trackInfo !== null) {
+            invoke("graph_set_parameter", {
+              trackId: trackInfo.trackId,
+              nodeId: nodeData.data.backendId,
+              paramId: 0, // rate parameter
+              value: hz
+            }).catch(err => {
+              console.error("Failed to update Phaser rate after BPM change:", err);
+            });
+            console.log(`Updated Phaser node ${nodeId} rate to ${hz} Hz for BPM ${newBpm}`);
+          }
+        }
+      }
+    });
+
     // Initialize minimap
     const minimapCanvas = container.querySelector("#minimap-canvas");
     const minimapViewport = container.querySelector(".minimap-viewport");
@@ -7679,11 +7761,41 @@ function nodeEditor() {
             if (nodeData.data.backendId !== null) {
               const trackInfo = getCurrentTrack();
               if (trackInfo !== null) {
+                // Convert beat divisions to Hz for Phaser rate in sync mode
+                let backendValue = value;
+                if (nodeDef && nodeDef.parameters[paramId]) {
+                  const param = nodeDef.parameters[paramId];
+                  if (param.name === 'rate' && nodeData.name === 'Phaser') {
+                    const syncCheckbox = nodeElement.querySelector(`#sync-${nodeId}`);
+                    if (syncCheckbox && syncCheckbox.checked && context.timelineWidget) {
+                      const beatDivisions = [
+                        { label: '4 bars', multiplier: 16.0 },
+                        { label: '2 bars', multiplier: 8.0 },
+                        { label: '1 bar', multiplier: 4.0 },
+                        { label: '1/2', multiplier: 2.0 },
+                        { label: '1/4', multiplier: 1.0 },
+                        { label: '1/8', multiplier: 0.5 },
+                        { label: '1/16', multiplier: 0.25 },
+                        { label: '1/32', multiplier: 0.125 },
+                        { label: '1/2T', multiplier: 2.0/3.0 },
+                        { label: '1/4T', multiplier: 1.0/3.0 },
+                        { label: '1/8T', multiplier: 0.5/3.0 }
+                      ];
+                      const idx = Math.min(10, Math.max(0, Math.round(value)));
+                      const bpm = context.timelineWidget.timelineState.bpm;
+                      const beatsPerSecond = bpm / 60.0;
+                      const quarterNotesPerCycle = beatDivisions[idx].multiplier;
+                      // Hz = how many cycles per second
+                      backendValue = beatsPerSecond / quarterNotesPerCycle;
+                    }
+                  }
+                }
+
                 invoke("graph_set_parameter", {
                   trackId: trackInfo.trackId,
                   nodeId: nodeData.data.backendId,
                   paramId: paramId,
-                  value: value
+                  value: backendValue
                 }).catch(err => {
                   console.error("Failed to set parameter:", err);
                 });

src/nodeTypes.js

@@ -1283,6 +1283,33 @@ export const nodeTypes = {
     `
   },
 
+  BpmDetector: {
+    name: 'BPM Detector',
+    category: NodeCategory.UTILITY,
+    description: 'Detects tempo from audio and outputs BPM as CV',
+    inputs: [
+      { name: 'Audio In', type: SignalType.AUDIO, index: 0 }
+    ],
+    outputs: [
+      { name: 'BPM CV', type: SignalType.CV, index: 0 }
+    ],
+    parameters: [
+      { id: 0, name: 'smoothing', label: 'Smoothing', min: 0.0, max: 1.0, default: 0.9, unit: '' }
+    ],
+    getHTML: (nodeId) => `
+      <div class="node-content">
+        <div class="node-title">BPM Detector</div>
+        <div class="node-param">
+          <label>Smoothing: <span id="smoothing-${nodeId}">0.90</span></label>
+          <input type="range" data-node="${nodeId}" data-param="0" min="0.0" max="1.0" value="0.9" step="0.01">
+        </div>
+        <div class="node-info" style="font-size: 10px; color: #888; margin-top: 5px;">
+          Analyzes incoming audio and outputs detected BPM as CV signal
+        </div>
+      </div>
+    `
+  },
+
   EnvelopeFollower: {
     name: 'Envelope Follower',
     category: NodeCategory.UTILITY,