There are four tracks , each has an arming button (Green) and seven leds. Top four are Mute Overdub Multiply and Solo , then below the button theres Record and Play , and below them in the middle an led to show the track is armed.
The other buttons from top left are Redo , Undo , Mute , Overdub, Record/Play, Multiply , Solo , Volume Down , Volume Up. These take effect on whichever track is armed.
Just finished it and I think all the code for the Arduino works as it should , Solo switches on Mute led on other tracks etc etc..
The leds are different colours,, in the photo they look alike but it shows yellow solo on plus blue mutes , red record and track orange. The yellow, red and orange look the same in the picture but that's just my camera.
There are about 16 spare pins on the arduino , so I could have made it 6 track but 4 seems plenty. I could also have used some of the other keystroke commands and put more switches to trigger them , once I'd got the code sorted it's quite simple.
I'll put the code and build up at Instructables and/or the Arduino projects pages someday soon.
Not sure if these images work. This does..
https://ibb.co/5sNwD8z