I got the music from Incompetech (which I am very familiar with; it is completely safe and even works cross-origin, e.g. in my Royalty Free Music Repertoire), but I used an MP3 compressor that I haven't used before (see I need music!). The compressed MP3 files (and the original) played in Snap! for me, so I think the issue is in SirHopsALot's computer or browser.