AY music files are memory dumps from ZX Spectrum 128 and CPC demos and games. The name comes the the sound chip inside these machines AY-3-8910.
|ProjectAY.zip||Copy of archive hosted at http://www.worldofspectrum.org/projectay/. Website is still online as of writing this, and backup was ajoured january 2020.|
Adlib / OPL music
A the adplug webpage, there is an extras section for where to find OPL/adlib music. Unfortunately, all of the links are dead. This is what I have been able to source looking around.
|adlib.superfighter.com.zip||Old arhive of https://adlib.superfighter.com. Website is still online, but only some few songs are listed.|
|AEGISPLAYER.zip||Origin is unknown. Contains .HSP files. Let me know if you know the history of these.|
|cta-adlib.zip||http://chiptunes.back2roots.org / http://chiptune.de archive using Internet Archive; Wayback Machine.|