Every Spinal Cord Injury is different. I fractured my T7 vertebrae and pretty well smashed my T12. I also broke my left scapula in two places and injured the nerves that run through the scapula. Broke two ribs, too. The injury resulted in complete paraplegia; no feeling or voluntary movement from the waist down. I hit my head pretty good too but still seem to be able to keep my train of thought.
Let's see... where was I? Oh, yes. Luckily, I have good use of my upper body which means I can still play the cello. Hmm... Doesn't sound very good, but I think that might be because I haven't practiced for a while.
To play, I should transfer to a normal height chair so my feet are flat on the floor. (See pic #1) That would stabilize my body better. It wouldn't add to a performance if I fell over like Humpty Dumpty.
The chair must be padded like my wheelchair to protect my tailbone. My natural cushion (gluteous maximus) is disappearing because of muscle atrophication. Ten minutes sitting on the wrong surface could give me a terrible sore that could send me to bed for months.
I'm pretty lucky. I can still play the cello without adaptation except for sitting on a special cushion. I could play the piano except for the foot pedal(s). I guess I could make a pressure sensitive mouth switch. That, and I'd Really have to practice. I never was a good pianist!