The music disk Apple II PT3 Player was not too long ago uploaded to Pouet.net.
It is really good and I advocate that you verify it out. 🙂 The author has uploaded a video of the complete production on YouTube, which is excellent for us who does not have the needed hardware to run it.
Longer demo of the Vortex Tracker PT3 player, recorded on an Apple IIe with Mockingboard card. Written in 6502 assembly language.