I've included a few WAV files for you to download and reverse. Because of the flaky behavior of the PyGame sound mixer, you may need to and close re-launch IDLE3 to test your code each time you modify it. I avoided this hassle by running the script from the terminal window:
  python3 tester11.py
The Stairway to Heaven clip is in stereo, so you can get extra credit if your playreverse works with it. But the results are pretty disturbing! Here is a little script that will test this clip in a way that doesn't interfere with the orindary (mono) clips.