Softsynths on the Apple 2 actually predate softsynths on both Spectrum and IBM PC! Lo and behold, the mighty Electric Duet:
https://arachnoid.com/electric_duet/

Unfortunately not: https://www.pouet.net/prod.php?which=87465 https://github.com/AYCEdemo/pettan
You're definitely the first to make a proper native tracker for the thing though!

For curiosity, I've dumped my old engines here: http://irrlichtproject.de/downloads/a2snd.zip No guarantees whatsoever, I haven't looked at this code for years and I have no memories of how functional/complete it actually is.

I wasn't aware that anyone had done softsynths for the Apple. I thought I was the first to do it on a 1MHz 6502 on the PET! I'd be interested to see how they work; I had a great deal of difficulty fitting 3.5 channels into the available CPU time, and that was with using a 6522's shift register to do much of the heavy lifting.

That reminds me, I actually have a couple of unreleased Apple II engines laying around! Never released them because I could never work out a way of building disk images that don't involve adding some proprietary blobs, but I think things have been moving in that domain in recent years. So I should get those out some day... Nothing fancy, just boring standard stuff, though.

https://www.youtube.com/watch?v=XSCKzUER7VY