Thx, man! In the long run probably something like 12U. Will start with 6U by building a 2x case, throw some power in, then get a couple modules, and start from there. I think the ER-101 will be the biggest outset in terms of cash. So I'll probably start with a VCO or two, envelop, maybe a filter or waveshaper, VCA: just basic meat and potatoes to learn how a synth voice works. Then just flesh it out from there.
What's so great is that you hear composers like Caterina Barbieri using some of the same process music method developed during. Process music is a form of minimalism that arises from a process, usually a very strict process. If you listen to interviews of Ms. Barbieri, she talks about an approach very similar to methods first pioneered back in the 1960s.