Some secrets of good musicians : the physics controlling articulation and timbre in reed instruments

![CDATA[Sometimes, the beauty of a single note identifies a good musician: The initial and final transients are controlled appropriately, as is the harmonic content of the sustained part. This study reports first how several control parameters are varied by accomplished players of clarinet and saxophone. It then uses measurements on a clarinet-playing machine to determine the effects of these parameters independently. In the sustained part of a note, mouth pressure P and lip force F applied to the reed affect both sound level and harmonic content. Further, good players can control the spectral envelope using the vocal tract: peaks in the acoustic impedance of the tract enhance the amplitude of harmonics in the played note at nearby frequencies. The highly salient initial transients produced by good human players have an approximately exponential increase in the amplitude of the fundamental at rates r about 1000 dB.s-1 that is achieved by varying both the rate of increase in P and the timing of tongue release during this increase. On the playing machine, when P is above the oscillation threshold, initial reed displacement decays quickly after tongue release, but tongue release rapidly changes the airflow into the bore. This initiates an exponential increase in the sound at rates r that can range from several tens to several hundreds of dB.s-1, and that, over the range used, increase with increasing P and decreasing F. Finishing notes either by decreasing P below a threshold, or by tongue contact with the reed, produces an exponential decay in the final transient. The amplitude of the fundamental decreases exponentially at rates -400 dB.s-1 when notes are stopped by human tonguing. This is consistent with the measured bandwidths of the bore resonances, which indicate the dissipated energy. A simple energy accounting model explains the exponential rises and falls in the initial and final transients: A static flow-pressure curve for the mouthpiece has positive and negative slopes corresponding to positive and negative AC conductances respectively. In the playing region, negative AC conductance converts steady pressure from the DC flow into acoustic energy. This oscillatory energy contributes to the energy stored in the reactive components of a resonance in the bore, from which the losses in the bore and the reed are sinks. The energy budget produces the observed behaviours.]]