Good information here thanks Alan. I only have one Melodica that really smells bad, it’s a Hohner Piano 20 1970s model I think. Mint condition but I am pretty sure it was stored in a cafe or a home where many cups of coffee were made and much tobacco smoking took place.
As a recovered (ex) smoker, I find it very difficult to play or handle the Piano 20 for very long as the odour makes my eyes water and my head swim. I tried rubbing alcohol which stopped the smell a little but baking soda was the missing link for me.