Uses a special trick to
get high quality NES music for the small file size.
The square waves and triangle wave are extracted as separate wav files. They are included in the .swf as RAW format audio events. Then Flash 6's gzip compression kicks in, and the file becomes much much smaller. Like from 12 megs to <150k.
The file would be a lot smaller if it weren't for the mp3 format audio stream which contains the noise and DMC channels.