Audio interrupt priority = 208

teensy3/AudioStream.cpp

 bool AudioStream::update_setup(void)
 {
 	if (update_scheduled) return false;
-	NVIC_SET_PRIORITY(IRQ_SOFTWARE, 0xFF); // 0xFF = lowest priority
+	NVIC_SET_PRIORITY(IRQ_SOFTWARE, 208); // 255 = lowest priority
 	NVIC_ENABLE_IRQ(IRQ_SOFTWARE);
 	update_scheduled = true;
 	return true;

teensy3/AudioStream.h

 typedef struct audio_block_struct {
 	unsigned char ref_count;
 	unsigned char memory_pool_index;
+	unsigned char reserved1;
+	unsigned char reserved2;
 	int16_t data[AUDIO_BLOCK_SAMPLES];
 } audio_block_t;