Popular & Traditional
Tremolo-tuned harmonicas are mainly used for folk music. They are easily recognisable by the horizontal division of the air channels. Each channel has two reeds for each note, one pair of blown notes and another pair for drawn notes. These reeds - which are basically identical - are tuned to slightly different frequencies. When played together, this difference causes the characteristic beating of the tremolo sound, a guarantee for a cheerful and merry tone!
Unlike the standard ten-hole harmonicas (built on the "Richter system", e.g. Hohner's Marine Band) the blow and draw reeds do not share a common chamber, but are separated off from one another. This allows the player to isolate each reed. It is also possible to play without the tremolo effect by only choosing the top or bottom chambers and blocking off the others with the lips. In practice, though, these are primarily used for effects and mostly the instrument is played as if the two beating reeds shared a single chamber.