techno
 

Any suggestions for the best FOSS solution for music composition (namely the creation of techno)?

I don't know about techno specifically (not my cup of tea - I thought techno composers just used Atari STs and four track sequencers - Har har).

Seriously though, if you're looking for some sort of sequencer, maybe take a look at LMMS. If you want to do serious multi-track stuff maybe have a look at Ardour (it's complex though). There's also a nice drum machine called Hydrogen.

Probably not what you want, but maybe also consider having a look at rosegarden.