realtime music-makin' software for my piece-of-shit PC?

I've got my shit ol' 300mHz with fuck all RAM plugged into my stereo running Rebirth, it runs really smoothly and I can fuck round with its twin synths and twin drum machines in realtime while jammin' round on my six-string which is also plugged into the stereo (sold my amp years ago, through my stereo it sounds remarkably good though - it helps that there's an "echo" (i.e. variable delay - ranging from subtle reverb to BA-ba-ba echo) and input level (which I've been using to create a surprisingly tolerable overdrive/distortion effect) on the mic input). Extraordinarily good fun. Any recommendations for other software synths etc. that I can run and tweak in realtime through this computer-museum specimen?

(not trackers, I'm not in the mood for "composing" prior to actually making a racket on the fly)

you can run reaktor V3 on that machine.

You'll get the most power out of a soft sampler synth such as Kontakt. I used a PII 333mhz and the main software I used was Kontakt 1 and I was able to get a good 10+ channels of decent sounds from it.

Hard part is finding a copy of a version that old.

Impulse Tracker

thanks for the tips, I'll try and look into these.

(lately I've been thinking about going "cheapcore" and getting hold of a cheap ancient laptop to lug around, running outdated music software in a band situation)

yeah, most older trackers should run nicely. you can also run Fruity Loops 3 - i used to run that on an IBM Aptiva P166 with 97MB RAM - i could only use one VST plugin at any one time though..... but for drum and keyboard hit samples, it's a really powerful sequencer and has real time control over all the parameters (on any samples too).