tlr made C64-demos in 1986 (!) and coded the Vic20-tracker VIC-tracker and Over5 for Amiga. Among other things, he now works with the VICE-emulators and it seems that he figured out a new trick with the oscillators of the 6560-chip inside Vic20. This music sounds cleaner and more perfected than other Vic20-music. Whereas other music uses the built-in 7-bit scale, which gives it the characteristic slightly-out-of-tune feeling, this uses 9-bit frequency resolution with fancy vibrato. The player also offers 6-bit pulse width modulation, and it all adds up sounding more like new Atari ST-music than Vic20, if it wasn’t for the noise-channel uses. Get mp3, prg, and info at this denial-forumpost.
Meanwhile, also in Stockholm, TBC has been developing a similar improvement of the frequency resolution for his new Vic20-game, which you can read about here. My favourite Vic20-soundhack is Viznut’s “speech synthesis” that take soundchip-hacking towards destabilizing aesthetics rather than perfection. Robotic Liberation gives me satisfaction.