ArduinoLowPower causes ArduinoSound to CRASH

Calling the LowPower.sleep(…) function from the ArduinoLowPower library causes I2S audio playback using the ArduinoSound library to crash.

The sketch below is based on the WavePlayback demo sketch, with a small delay between playbacks. If delay() is used, the sketch works as expected. However, if LowPower.sleep(…) audio playback crashes.

Any ideas or suggestions would be most welcome.

Thank you

 This reads a wave file from an SD card and plays it using the I2S interface to
 a MAX08357 I2S Amp Breakout board.

 * Arduino/Genuino Zero, MKRZero or MKR1000 board
 * SD breakout or shield connected
 * MAX08357:
   * GND connected GND
   * VIN connected 5V
   * LRC connected to pin 0 (Zero) or pin 3 (MKR1000, MKRZero)
   * BCLK connected to pin 1 (Zero) or pin 2 (MKR1000, MKRZero)
   * DIN connected to pin 9 (Zero) or pin A6 (MKR1000, MKRZero)

 created 15 November 2016
 by Sandeep Mistry

#include <SD.h>
#include <ArduinoSound.h>
#include <ArduinoLowPower.h>

// filename of wave file to play
const char filename[] = "SONG0.WAV";

// variable representing the Wave File
SDWaveFile waveFile;

void setup() {
  // Open serial communications and wait for port to open:
  while (!Serial) {
    ; // wait for serial port to connect. Needed for native USB port only

  // setup the SD card, depending on your shield of breakout board
  // you may need to pass a pin number in begin for SS
  Serial.print("Initializing SD card...");
  if (!SD.begin()) {
    Serial.println("initialization failed!");
  Serial.println("initialization done.");

  // create a SDWaveFile
  waveFile = SDWaveFile(filename);

  // check if the WaveFile is valid
  if (!waveFile) {
    Serial.println("wave file is invalid!");
    while (1); // do nothing

  // print out some info. about the wave file
  Serial.print("Bits per sample = ");

  long channels = waveFile.channels();
  Serial.print("Channels = ");

  long sampleRate = waveFile.sampleRate();
  Serial.print("Sample rate = ");
  Serial.println(" Hz");

  long duration = waveFile.duration();
  Serial.print("Duration = ");
  Serial.println(" seconds");

  // adjust the playback volume
  AudioOutI2S.volume( 50 );

  // check if the I2S output can play the wave file
  if (!AudioOutI2S.canPlay(waveFile)) {
    Serial.println("unable to play wave file using I2S!");
    while (1); // do nothing


void loop() {

  // start playback
  Serial.println("starting playback");;  
  do {  
    // wait
  while ( AudioOutI2S.isPlaying() );

 * Using delay(..) works as expected
 * Using LowPower.sleep(..) causes audio playback to stop working




Serial.println("Playing file again ");;

  do {  
    // wait
  while ( AudioOutI2S.isPlaying() );


@whitear's issue report: