I recently remembered an OPL3 instrument editor for DOS which had an interesting feedback guitar as one of the presets. I've been looking all over for it but cannot find it anywhere... even cd.textfiles.com doesn't have it.

It featured 4 tiled windows with adjustable envelopes. I think It was red windows over black with white text. It was definitely 16-color 640x400 VGA. I think I got it from what I think was the first big DOS shareware site which tried to imitate DOS's character-oriented windows design language by using among other things a fixed width font and EGA-colored windows. It resembled a DOS program and I'd look it up on Wayback but I don't remember the name of the site!