Best Software For Dnb/industrial/noise Music? Options

[Darwinist]

I´d like to try my hand at creating DnB/industrial/noise music on my 450mhz iMac, but I don´t want to fill up my room with gear or spend too much money.

I´m basically looking for shareware/freeware programs to play around with, something to create beats, synth lines and some good distortion effect to make it sound really evil. Ideally I´d like something simple, yet open-ended, where you can just fiddle around with things until you hit on something you like. And capeable to handle both samples and synthesis.

Any suggestions appreciated.