Inspired by https://www.lexaloffle.com/bbs/?tid=2341, here's a description of how sfx and music are stored in Picotron. (Well, there's not much description here yet, just some helpful code. I'll add to this over time)
The data can be in unusual custom formats. The header data is supposed to help in these cases and is accounted for in this code (with some asserts to crash if the data format is unknown). But for most people using this code, the data will be in the standard format.
Sources: