Players coordinate tongue release and variation in blowing pressure to produce a range of desired initial transients, e.g. for accents and sforzando, players use higher pressures at release to give higher rise rates in the exponential phase. The mechanisms were studied with high-speed video and acoustic measurements on human and artificial players of clarinets and simpler models. The initial mechanical energy of the reed due to deformation and release by the tongue is quickly lost in damping by the lip. The varying aperture as the reed moves towards equilibrium produces proportional variations in flow and pressure via a mechanism resembling the water hammer in hydraulics. Superposition of this signal with returning reflections from the bore give complicated wave shapes with variable harmonic content. When the reed gain more than compensates for losses, a nearly exponential phase follows until the last few oscillations before saturation. Maximal exponential decay rates (in tongue-stopped staccato notes) agree with losses measured in the bore impedance spectrum. Including estimates of the negative reed resistance explains semi- quantitatively the rise rates for initial transients. Different rates for higher harmonics contribute to different wave shapes and spectral envelopes, which are illustrated and modelled here.
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