diff --git a/src/core/midi.rs b/src/core/midi.rs
index be8715ed..6caada72 100644
--- a/src/core/midi.rs
+++ b/src/core/midi.rs
@@ -7,18 +7,15 @@ pub type MIDIMessage =
     Vec<u8>;
 
 pub type MIDIChunk =
-    [Option<Vec<MIDIMessage>>];
+    [Vec<MIDIMessage>];
 
 /// Add "all notes off" to the start of a buffer.
 pub fn all_notes_off (output: &mut MIDIChunk) {
-    output[0] = Some(vec![]);
-    if let Some(Some(frame)) = output.get_mut(0) {
-        let mut buf = vec![];
-        let msg = MidiMessage::Controller { controller: 123.into(), value: 0.into() };
-        let evt = LiveEvent::Midi { channel: 0.into(), message: msg };
-        evt.write(&mut buf).unwrap();
-        frame.push(buf);
-    }
+    let mut buf = vec![];
+    let msg = MidiMessage::Controller { controller: 123.into(), value: 0.into() };
+    let evt = LiveEvent::Midi { channel: 0.into(), message: msg };
+    evt.write(&mut buf).unwrap();
+    output[0].push(buf);
 }
 
 pub fn parse_midi_input (input: MidiIter) -> Box<dyn Iterator<Item=(usize, LiveEvent, &[u8])> + '_> {
@@ -32,11 +29,9 @@ pub fn parse_midi_input (input: MidiIter) -> Box<dyn Iterator<Item=(usize, LiveE
 /// Write to JACK port from output buffer (containing notes from sequence and/or monitor)
 pub fn write_midi_output (writer: &mut ::jack::MidiWriter, output: &MIDIChunk, frames: usize) {
     for time in 0..frames {
-        if let Some(Some(frame)) = output.get(time) {
-            for event in frame.iter() {
-                writer.write(&::jack::RawMidi { time: time as u32, bytes: &event })
-                    .expect(&format!("{event:?}"));
-            }
+        for event in output[time].iter() {
+            writer.write(&::jack::RawMidi { time: time as u32, bytes: &event })
+                .expect(&format!("{event:?}"));
         }
     }
 }
diff --git a/src/model/phrase.rs b/src/model/phrase.rs
index 704ff32c..e6eddfd9 100644
--- a/src/model/phrase.rs
+++ b/src/model/phrase.rs
@@ -68,12 +68,7 @@ impl Phrase {
                 }
                 LiveEvent::Midi { channel, message }.write(&mut buf).unwrap();
                 let t = *time as usize;
-                if output[t].is_none() {
-                    output[t] = Some(vec![]);
-                }
-                if let Some(Some(frame)) = output.get_mut(t) {
-                    frame.push(buf);
-                }
+                output[t].push(buf);
             }
         }
     }
diff --git a/src/model/track.rs b/src/model/track.rs
index 4e7f921c..b3d1a04c 100644
--- a/src/model/track.rs
+++ b/src/model/track.rs
@@ -15,6 +15,7 @@ pub struct Track {
     pub sequence:   Option<usize>,
     /// Output from current sequence.
     pub midi_out:   Port<MidiOut>,
+    midi_out_buf:   Vec<Vec<Vec<u8>>>,
     /// Red keys on piano roll.
     pub notes_on:   Vec<bool>,
     /// Device chain
@@ -39,89 +40,30 @@ impl Track {
         devices: Option<Vec<JackDevice>>,
     ) -> Usually<Self> {
         Ok(Self {
-            name:       name.to_string(),
-            midi_out:   jack.register_port(name, MidiOut)?,
-            notes_on:   vec![],
-            monitoring: false,
-            recording:  false,
-            overdub:    true,
-            sequence:   None,
-            phrases:    phrases.unwrap_or_else(||Vec::with_capacity(16)),
-            devices:    devices.unwrap_or_else(||Vec::with_capacity(16)),
-            device:     0,
+            name:         name.to_string(),
+            midi_out:     jack.register_port(name, MidiOut)?,
+            midi_out_buf: vec![vec![];1024],
+            notes_on:     vec![false;128],
+            monitoring:   false,
+            recording:    false,
+            overdub:      true,
+            sequence:     None,
+            phrases:      phrases.unwrap_or_else(||Vec::with_capacity(16)),
+            devices:      devices.unwrap_or_else(||Vec::with_capacity(16)),
+            device:       0,
         })
     }
-    pub fn process (
-        &mut self,
-        input:    MidiIter,
-        timebase: &Arc<Timebase>,
-        playing:  Option<TransportState>,
-        scope:    &ProcessScope,
-        frame0:   usize,
-        frames:   usize,
-        panic:    bool,
-    ) {
-        // Need to be borrowed outside the conditionals?
-        let recording  = self.recording;
-        let monitoring = self.monitoring;
-        // Output buffer
-        let mut output: Vec<Option<Vec<Vec<u8>>>> = vec![None;frames];
-        // For highlighting keys
-        let mut notes_on = vec![false;128];
-        if panic { all_notes_off(&mut output); }
-        // Play from phrase into output buffer
-        if let Some(phrase) = self.phrase() {
-            if playing == Some(TransportState::Rolling) {
-                phrase.process_out(
-                    &mut output,
-                    &mut notes_on,
-                    timebase,
-                    frame0,
-                    frames
-                );
-            }
-        }
-        // Monitor and record input
-        if self.recording || self.monitoring {
-            let phrase = &mut self.phrase_mut();
-            for (time, event, bytes) in parse_midi_input(input) {
-                match event {
-                    LiveEvent::Midi { message, .. } => {
-                        if monitoring {
-                            if let Some(Some(frame)) = output.get_mut(time) {
-                                frame.push(bytes.into())
-                            } else {
-                                output[time] = Some(vec![bytes.into()]);
-                            }
-                        }
-                        if recording {
-                            if let Some(phrase) = phrase {
-                                let pulse = timebase.frames_pulses((frame0 + time) as f64) as usize;
-                                let pulse = pulse % phrase.length;
-                                let contains = phrase.notes.contains_key(&pulse);
-                                if contains {
-                                    phrase.notes.get_mut(&pulse).unwrap().push(message.clone());
-                                } else {
-                                    phrase.notes.insert(pulse, vec![message.clone()]);
-                                }
-                            };
-                        }
-                        match message {
-                            MidiMessage::NoteOn { key, .. } => {
-                                notes_on[key.as_int() as usize] = true;
-                            }
-                            MidiMessage::NoteOff { key, .. } => {
-                                notes_on[key.as_int() as usize] = false;
-                            },
-                            _ => {}
-                        }
-                    },
-                    _ => {}
-                }
-            }
-        }
-        self.notes_on = notes_on;
-        write_midi_output(&mut self.midi_out.writer(scope), &output, frames);
+    pub fn device (&self) -> Option<MutexGuard<Box<dyn Device>>> {
+        self.get_device(self.device)
+    }
+    pub fn first_device (&self) -> Option<MutexGuard<Box<dyn Device>>> {
+        self.get_device(0)
+    }
+    pub fn last_device (&self) -> Option<MutexGuard<Box<dyn Device>>> {
+        self.get_device(self.devices.len().saturating_sub(1))
+    }
+    pub fn get_device (&self, i: usize) -> Option<MutexGuard<Box<dyn Device>>> {
+        self.devices.get(i).map(|d|d.state.lock().unwrap())
     }
     pub fn add_device (&mut self, device: JackDevice) -> Usually<&mut JackDevice> {
         self.devices.push(device);
@@ -138,18 +80,6 @@ impl Track {
         let index = self.devices.len() - 1;
         Ok(&mut self.devices[index])
     }
-    pub fn get_device (&self, i: usize) -> Option<MutexGuard<Box<dyn Device>>> {
-        self.devices.get(i).map(|d|d.state.lock().unwrap())
-    }
-    pub fn device (&self) -> Option<MutexGuard<Box<dyn Device>>> {
-        self.get_device(self.device)
-    }
-    pub fn first_device (&self) -> Option<MutexGuard<Box<dyn Device>>> {
-        self.get_device(0)
-    }
-    pub fn last_device (&self) -> Option<MutexGuard<Box<dyn Device>>> {
-        self.get_device(self.devices.len().saturating_sub(1))
-    }
     pub fn phrase (&self) -> Option<&Phrase> {
         if let Some(phrase) = self.sequence {
             return self.phrases.get(phrase)
@@ -180,4 +110,80 @@ impl Track {
     pub fn toggle_overdub (&mut self) {
         self.overdub = !self.overdub;
     }
+    pub fn process (
+        &mut self,
+        input:    MidiIter,
+        timebase: &Arc<Timebase>,
+        playing:  Option<TransportState>,
+        scope:    &ProcessScope,
+        frame0:   usize,
+        frames:   usize,
+        panic:    bool,
+    ) {
+        // Need to be borrowed outside the conditionals?
+        let recording  = self.recording;
+        let monitoring = self.monitoring;
+        // Clear the section of the output buffer that we will be using
+        for frame in &mut self.midi_out_buf[0..frames] {
+            frame.clear();
+        }
+        // Emit "all notes off" at start of buffer if requested
+        if panic {
+            all_notes_off(&mut self.midi_out_buf);
+        }
+        // Play from phrase into output buffer
+        if let Some(Some(phrase)) = self.sequence.map(|id|self.phrases.get(id)) {
+            if playing == Some(TransportState::Rolling) {
+                phrase.process_out(
+                    &mut self.midi_out_buf,
+                    &mut self.notes_on,
+                    timebase,
+                    frame0,
+                    frames
+                );
+            }
+        }
+        // Monitor and record input
+        if self.recording || self.monitoring {
+            // For highlighting keys
+            let notes_on = &mut self.notes_on;
+            let phrase   = &mut self.sequence.map(|id|self.phrases.get_mut(id));
+            for (time, event, bytes) in parse_midi_input(input) {
+                match event {
+                    LiveEvent::Midi { message, .. } => {
+                        if monitoring {
+                            self.midi_out_buf[time].push(bytes.to_vec())
+                        }
+                        if recording {
+                            if let Some(Some(phrase)) = phrase {
+                                let pulse = timebase.frames_pulses((frame0 + time) as f64) as usize;
+                                let pulse = pulse % phrase.length;
+                                let contains = phrase.notes.contains_key(&pulse);
+                                if contains {
+                                    phrase.notes.get_mut(&pulse).unwrap().push(message.clone());
+                                } else {
+                                    phrase.notes.insert(pulse, vec![message.clone()]);
+                                }
+                            };
+                        }
+                        match message {
+                            MidiMessage::NoteOn { key, .. } => {
+                                notes_on[key.as_int() as usize] = true;
+                            }
+                            MidiMessage::NoteOff { key, .. } => {
+                                notes_on[key.as_int() as usize] = false;
+                            },
+                            _ => {}
+                        }
+                    },
+                    _ => {}
+                }
+            }
+        }
+        write_midi_output(
+            &mut self.midi_out.writer(scope),
+            &self.midi_out_buf,
+            frames
+        );
+    }
 }