diff --git a/PlaybackThread.cpp b/PlaybackThread.cpp
index 1bfa778..833281a 100644
--- a/PlaybackThread.cpp
+++ b/PlaybackThread.cpp
@@ -4,12 +4,15 @@
 #include "config.h"
 #include "SharedState.h"
 
+static Step local_sequence[NUM_TRACKS][NUM_STEPS];
+static Step local_nextSequence[NUM_TRACKS][NUM_STEPS];
+
 bool wasPlaying = false;
 
 static void handlePlayback() {
   bool nowPlaying = isPlaying;
   int tracksToPlay = (playMode == MODE_POLY) ? NUM_TRACKS : 1;
-  if (!wasPlaying && !nowPlaying) {
+  if (!wasPlaying && nowPlaying) {
     midi.sendRealtime(0xFA); // MIDI Start
   } else if (wasPlaying && !nowPlaying) {
     midi.sendRealtime(0xFC); // MIDI Stop
@@ -17,12 +20,18 @@ static void handlePlayback() {
   }
   wasPlaying = nowPlaying;
 
-  if (!nowPlaying) return;
+  if (!nowPlaying) {
+    delay(1); // yield
+    return;
+  }
 
   unsigned long currentMicros = micros();
   unsigned long clockInterval = 2500000 / tempo; // 60s * 1000000us / (tempo * 24ppqn)
 
-  if (currentMicros - lastClockTime >= clockInterval) {
+  if (currentMicros - lastClockTime < clockInterval) {
+    delay(1); // yield
+    return;
+  } else {
     lastClockTime += clockInterval;
     
     midi.sendRealtime(0xF8); // MIDI Clock
@@ -32,9 +41,7 @@ static void handlePlayback() {
     clockCount = 0;
 
     midi.lock();
-    Step local_sequence[NUM_TRACKS][NUM_STEPS];
     memcpy(local_sequence, sequence, sizeof(local_sequence));
-    Step local_nextSequence[NUM_TRACKS][NUM_STEPS];
     memcpy(local_nextSequence, nextSequence, sizeof(local_nextSequence));
     midi.unlock();
 
diff --git a/UIThread.cpp b/UIThread.cpp
index 9154be9..34ae679 100644
--- a/UIThread.cpp
+++ b/UIThread.cpp
@@ -15,7 +15,7 @@
 #include "UIThread.h"
 #include "SharedState.h"
 
-
+static Step local_sequence[NUM_TRACKS][NUM_STEPS];
 
 static void handleInput();
 static void drawUI();
@@ -106,8 +106,7 @@ static void generateSequenceData(int themeType, Step (*target)[NUM_STEPS]) {
 }
 
 void generateTheme(int themeType) {
-  Step local_sequence[NUM_TRACKS][NUM_STEPS];
-  generateSequenceData(themeType, sequence);
+  generateSequenceData(themeType, local_sequence);
 
   midi.lock();
   memcpy(sequence, local_sequence, sizeof(local_sequence));
@@ -353,7 +352,6 @@ static void drawUI() {
   bool local_trackMute[NUM_TRACKS];
   int local_midiChannel;
   MelodyStrategy* local_strategy;
-  Step local_sequence[NUM_TRACKS][NUM_STEPS];
   int local_playbackStep;
   int local_scaleNotes[12];
 
@@ -401,7 +399,6 @@ static void drawUI() {
 static void updateLeds() {
   // Make local copies of shared data inside a critical section
   // to avoid holding the lock during slow LED update operations.
-  Step local_sequence[NUM_TRACKS][NUM_STEPS];
   int local_playbackStep;
   bool local_isPlaying;
   UIState local_currentState;