Edit: maybe we should make a general "when did they use this and WHY" thread[/quote]
I like that idea...
I think this was posted some time back but there is a claim that the effects pedal The Emperor's Dirty Clothes Square Wave Distortion Effect was built for Sonic Youth by Graig Markel, of Recovery Effects.
http://www.youtube.com/watch?v=tjuwn18fbI0
Did the band ever use this? maybe in the studio? never seen or heard this used by anyone in the band... kinda neat effect, w/ a built in oscillator, sounds abit like the stab knob working on a ZVex fuzz factory (ZVex also has stated that Sonic Youth tried his effects at some point...)