Radio Shack Karaoke Machine - Echo Amp 88

These Radio Shack Karaoke Machines aren't as common as they used to be. I found this one (catalog Number 32-1156) 10 + years ago at a local thrift. It's been sitting in my collection collecting dust. I removed the cassette player and circuit bent the echo chip with three knobs & switches, plus 2 momentary buttons. No input feed-backer. I'm fumbling through the controls to see whats what?