A FYI follow-up. I have been testing with various (non-wav) audio files and have been using Audacity to convert them to .wav files and so far, all tests have been successful. All you need to do is get a free download of Audacity, select File-Open and load the input file. Then select File-Export, select (Microsoft) wav and save. Then put that .wav file on an USB drive and the GLD will gladly see/play it. Remember .wav files are NOT small, so would suggest a multi-gig USB drive. Also remember to initialize (using format) the USB drive (fat 32) and use default block size. I normally do NOT use fast format to be sure that the USB drive is good.