I would use mild soap and water, as always. Not too wet, don’t leave wet too long. Damp rag, follow with dry.
Peroxide is just water with a small amount of H2O2 (3% is normal off the shelf). That acts as a mild bleach, breaking down dyes (oxidizing them). So it is likely to make the color of wooden keys lighter, and if not applied carefully may leave mottled areas. I’d say alcohol would be preferable, less risky. Unless you have plastic keys.
Regards,
Fred Sturm
University of New Mexico
fssturm@unm.eduhttp://fredsturm.netwww.artoftuning.com“All of humanity's problems stem from man's inability to sit quietly in a room alone. ” Blaise Pascal