n normal woodwind tone production the nonlinear flow control properties of the reed transfer energy among the harmonics of the spectrum, and the favored playing frequency is one for which the air column input impedance is high at several harmonics. Above the middle of the second register, woodwinds have only one participating impedance peak; yet these notes can be played even without the use of a register hole, despite competing possibilities of low register intermode cooperation. Such notes are possible because enhancement of the reed’s transconductance A near its own resonance frequency can offset the small input impedance Z of the air column so that (ZA−1)≳0, providing an additional means for energy production above cutoff. Spectral levels as a function of blowing pressure, air column impedance, and reed characteristics are derived. Experiments on the clarinet show that the player can adjust the reed resonance frequency from about 2 to 3 kHz. When the reed frequency is adjusted to match a harmonic component of the tone, the amplitude of that component is increased, and the oscillation is heard as being stabilized in loudness, pitch, and tone color.