The tremolo harmonica is not as common among harmonica players compared to say the diatonic harmonica. Each reed is doubled to produce the tremolo effect that is very accordion like. Still it has extremely accurate and responsive reeds. It produces a nice delicate sound. The number of reeds a Tremolo may have range from 42-reed, 21-note tremolo harmonica to more or fewer reeds and notes. The tremolo has a plastic or wood comb and some models like the Suzuki SU-21H are available in multiple keys. The Tremolo Harmonica offers a consistently good sound, compared to other models of Harmonicas. Tremolo is both an easy to learn and a reliable instrument.