quite recently I cleaned up an older Hohner Cassotto 26.
It was in good condition but with a musty smell and with squeaky and clunky keys.
I disassembled it and bathed all parts a few minutes in warm water with some dish liquid. After that I rinsed it with pure warm water and led all parts dried over night.
After that I lubricate the valve shafts with a bit Vaseline and reassembled the instrument.
After that it nearly feels like new, no squeaky and much less clunky keys, also the smell is nearly gone.
A three to one (or 2-1) mix of water and common distilled (unflavored) vinegar is the usual solution for washing the melodica,
I threw the two parts in my kitchen sink with about 50/50 mix of warm water and vinegar, and a touch of dish soap. They were in the water for about 30 minutes
Actually i followed some advices here and it didn’t turn too well for my Hohner26 painting .. i guess my white vinegar 6% was not a good choice ahah. But the smell dissapeared for good, and it’s still functional. Any hints for bathing my second melodica? (same model)