I just built this, and I get the squeal and sometimes the motorboating. It's still attached to the breadboard, and one thing I noticed is that when it squeals and I touch the tonepot (which has no knob on it), the squeal is slightly but noticeably reduced. Maybe there's a grounding aspect to the squeal?
I used an ICL7660S and TL072's.
I used an ICL7660S and TL072's.