[Alan Brinton]

There seem to be three main kinds of springs used for key tension on melodicas: Extension Springs, Compression Springs, and
Torsion Springs.

Extension:

Compression:

Torsion:

The extension spring is stretched. This kind of spring is usually fairly easy to remove and replace. Tension can be reduced by slightly stretching the spring and increased by clipping off a loop or two. An extension spring can usually be replaced by one of similar size and gauge, with some adjustment. The compression spring, as found on the Clavietta, is compressed with pressure on both ends. In a melodica, it is likely to be adjustable with screw or nut on one end. It is very easy to lose this kind of spring since when the pressure is released at one end, it will launch itself off into the distance. It is best to remove and replace these within an enclosure. The torsion spring is hardest to work with. It typically is compressed under the key, making it harder to remove and replace keys and to get the spring into place. Tension can be increased by pulling the ends of the spring apart or compressing them together. It seems to be harder to get this just right than with the other types.