organfairy demos cleaning up a used Casio MT-110 keyboard to make it usable:

I got this little Casio MT-110 at a charity sale. It works fine but unfortunately somebody had put stickers on the keys which made them all sticky and gooey. On top of that the instrument was quite dusty and greasy – like if a kid had played it immediately after eating a jam sandwich (and yes, that is often the case with second hand toy keyboards).
So I took it apart. Cleaned all the parts. And assembled it again.

Again the music is something I made in 1997. It is played on Roland SH-2000, Casio SA-1, Casio SA-3 with Boss OC-2 octaver, Kawai MS-20, and Yamaha PSS-12, and Roland CR-1000.