using d65010g31 sound chip from Casio PV-1000 game console (from mame) - perhaps it has some potential for a new format one day soon?
(d65010g31 (still not supported from vgm format) is a 3-channel sound chip like sn76489 and ay-3-8910, but has no noise, no volume registers, and 6 bits for frequencies (instead of 12 from ay-3-8910, or 10 from sn76489) )
(song made on SnevenTracker, converted .txt file to code - .bin compiled from Boriel's ZX-Basic Compiler (i use it for everything running on z80 cpu), with some help from a bash script with some dd command lines)