In the 1970's, I remember going to a Kustom product demo outside of Philadelphia, near Cherry Hill, NJ. It was held at a hotel ballroom with a lot of people attending, and it featured a popular musician at the time. He was a blind keyboardist who was mainly demoing a new Kustom mixer and PA system through which he played electronic keyboards. He was great. The sales rep was very good. I remember him referring to the old Kustom "rolled and pleated" and this was the newer tolex covering.
He was in his late thirties, maybe early forties. Jazz oriented. Hair below his ears but above his shoulders. I wish my memory on this was better. I remember just how good he was at making adjustments on the mixer.
I found the answer to my question. It was Mike Mandel and he played keyboard for Larry Coryell in the early 1970's. Thanks to all that responded.
I was reading some articles about him. His recording studio, being blind but walking without a cane and not wearing sunglasses.
I just remember that when he did the kustom demo, he was really comfortable reaching for the controls. He knew where EVERYTHING was. Quite amazing to watch.