[sdiy] intro to SDIY playshop: suggestions?

[rdrake]

i've been facilitating (i hesitate to say "teaching") a workshop in musical/noize electronics, based primarily on Nic Collins' fantastic "Handmade Electronic Music" book.  most of the participants started with zero technical knowledge.  so far they've learned some soldering, basic components & schematics, circuit bending, solderless breadboards, and built a contact mic, LM386 amp, and a variety of CMOS oscillators (40106, 4093).  really has been a ton of fun, and very gratifying to see folks pick up on stuff.

now that we have some sound sources, i'd like to introduce some kinds of sound modifying circuits... in part to quiet that infernal beeping din.  homemade 'vactrol' kinds of things being the obvious choice.  thought i'd ask for suggestions, for VCA, VCF, or other such?  requirements are to be dead simple, fault-tolerent, non-critical component values... and my preference would be to stick with single-sided supply, everything so far has been 9v.

just for context: folks goals are to get a general pragmatic orientation to electronics (not intro EE, just enuf to make stuff work), and to make noize (not necessarily "music"--beeping is fine, tuning is optional).  i showed a reverb made out of a slinky glued to a speaker on one end and a piezo on the other, met with widespread approval)...  

anyway, would welcome suggestions.  

bbob
www.fluxmonkey.com