One can play chromatically on a diatonic harmonica by using different playi
ng modes: normal playing, bends and overnotes (overblows and overdraws). Fo
r each playing mode, the reed motions were measured with strain gauges and
the inner pressures were recorded at the same time with a differential pres
sure transducer. The reed motions were shown to be sinusoidal. The control
of active reed motion(s) on the evolutions of the inner pressure was underl
ined. The internal mechanisms occurring during playing were systematically
analyzed. Modelling of the reeds operation was derived and explanations for
the harmonic content of the sound is given.