This is something i learned digging about in my TF2 files.
(Note, Post-Steam-Pipe they all appear to be in C:\Program Files (x86)\Steam\steamapps\common\Team Fortress 2\tf\download\sound
Often, When you visit non-oficcial TF2 servers, They download a bunch of almost never used files for things like either sound effects, But sometimes you can get totally legitimate music from this, Just dig around in the directory above and look for .MP3 files
(Note, Post-Steam-Pipe they all appear to be in C:\Program Files (x86)\Steam\steamapps\common\Team Fortress 2\tf\download\sound
Often, When you visit non-oficcial TF2 servers, They download a bunch of almost never used files for things like either sound effects, But sometimes you can get totally legitimate music from this, Just dig around in the directory above and look for .MP3 files