lmemsm

Here are some links related to music documentation.

URLs are accurate as of when this was posted. However, they can change over time. You can use a search engine or archive.org wayback tool to find pages that have been moved or backups of older versions of pages.

Music Theory for Musicians and Normal People
Creative Commons licensed music theory PDF.
http://tobyrush.com/theorypages/index.html

Programming and Using Linux Sound - in depth
Nice introduction to music software on Linux.
Has some good coding examples using midi code such as TiMidity++ and other midi libraries.
https://jan.newmarch.name/LinuxSound/

Recipes for Music on Your PC
Tutorial on creating music using ABC notation and TiMidity++
http://distasis.com/recipes/music.htm

Wotsits.org sound and music file formats
File format information backed up at archive.org from the no longer available wotsits.org site
https://web.archive.org/web/20150323133016/http://www.wotsit.org/list.asp?fc=12