Traceback (most recent call last):
File "<stdin>", line 26, in <module>
File "<stdin>", line 18, in loop
OSError: [Errno 2] ENOENT

a snippet of the code from the Python side of things:

def setup():
  global rgb

  M5.begin()
  Widgets.setRotation(1)
  Widgets.fillScreen(0x222222)

  rgb = RGB()
  Speaker.begin()
  Speaker.setVolumePercentage(0.5)


def loop():
  global rgb
  M5.update()
  Speaker.playWavFile('/flash/res/audio/test1.wav')
  if Speaker.isPlaying():
    rgb.fill_color(0xffffff)
  time.sleep(2)

No code I've downloaded from other people works either! I can play tones out of the speaker, I can read images out of flash. I cannot read audio files out of flash.