Octave harmonica
Octave harmonicas are a type of harmonicas that have two reeds per tone, which are intoned shifted by exactly one octave . Many of them are identical in construction to that of a tremolo harmonica and are based on the “Vienna System”. Octave harmonicas are also built according to the "Knittlingersystem". In this construction, the upper as well as the lower reed includes all draw and blow tones of either higher or lower pitch. The comb is designed so that the pull and blow tongues are next to each other on the reed, as is the case with a standard diatonic harmonica.