With those of Coltman. Blowing pressure and jet length come near to satisfying the expected relationship but with some discrepancy which may be significant. Harmonic analysis of flute tone shows that amplitude variations from piano to forte are largely confined to the upper partials, particularly for notes in the low octave. A study of vibrato shows that this normally consists of an amplitude modulation of the upper partials of the tone with little change in the fundamental. The vibrato frequency is consistently about 5 Hz and is associated with a 10% variation in blowing pressure at that frequency. Physiological