In wind instruments, reeds (including lip reeds) interact with the acoustic impedances of the instrument's bore, Zb and the player's vocal tract, Zt. The bore is usually narrow and has high Q resonances whose maxima in Z b are large and determine the playing regime to first order. The tract has resonances with lower Q which act on a small area of the reed. So how do the weak maxima in Zt affect the timbre and pitch? We answer this question using a mechanical reed with geometrically simple vocal tracts and lungs to model didjeridu and trombone players. The small area of the reed (or moving area of the lips) 'sees ' only weak tract resonances (Zt << Zb) if the tongue is low. The tongue, when raised at the tip, acts as an impedance matching transformer linking this small area to the larger cross sectional area of the lower tract. Different tract configurations give strong effects on timbre and considerable effects on intonation, independently of the reed. The effects are consistent with those reported by players and explain some known intonation effects. 1
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