Not a build, but a sudden idea 
“name of zeus, Marty” 
I think about a modification on an ISD1820 Looper/Sampler i’ve done.
He have an LFO with a CD4040 for speed divisions controled by body contacts.
I like this FX but it can need 6 fingers, so many fingers that cannot play with others things.
I will try tomorow to add a serie of switch with some resistors, maybe a pot to trigger and hold this FX without my body contact.
I’m just happy with this and share it, now it’s the night for me.