So, I was practicing the scale and I happened to go from Low E to High B, but when I let go of the octave key, the High B persisted, only a bit higher. It does this with every note (haven’t tried the sharps and flats) up to Middle E. I have provided a video to better illustrate my point. The notes played are Low E, High B and the other note that occurs when the octave key is released.


2 Answers 2


Opening the register key, or allowing any leak from the top part of the instrument will set off the higher note (the twelfth), with the register key method having the best intonation. The higher register note continues to sound until dampened slightly. Typically dropping the jaw to allow some of the lower lip to dampen the reed vibration will make the clarinet sound it’s fundamental pitch again. This is also the method of slurring down from the upper to lower registers. Therefor, fingering is not merely enough to play the clarinet, as the embouchure and reed is integral to producing the correct pitch.

  • So, the reason the note persisted is because I didn’t change my mouth position?
    – user54267
    Commented Nov 14, 2018 at 11:52
  • 1
    Precisely. The reed will continue its higher energy vibration unless acted upon to remove some of that energy. Sometimes the acoustic impededance of the long clarinet tube is enough to change down to the lower register. Other times, a quick adjustment of the embouchure is required. Commented Nov 14, 2018 at 12:09
  • To be precise -- once the octave key is closed, a small amount of "noise" in the audio spectrum will quickly lead to resonant enhancement of the base note, thus "stealiing" energy from the overtone. Electrical engineers understand this as a resonant circuit. Commented Nov 14, 2018 at 13:30

The octave/register key is not strictly required in order to play the notes in the second octave/register of a woodwind instrument, it merely makes them dramatically easier. The tiny hole it opens prevents the first harmonic from forming, causing the second (or third in the case of clarinet) to be the lowest frequency the tube can resonate. On saxophone, playing higher harmonics without the octave key is a basic exercise towards learning altissimo.

The octave/register vent will act as a tone hole as well, however. It's made as small as possible in order to minimize this, but the effect is an inevitability of physics. In fact, the standard Bb fingering of A key + register key uses the register vent for exactly that purpose. On a note like long B, the register vent causes the pitch to shade upwards slightly, which is what you're observing.

  • I still don’t understand why the note kept playing. Would it not revert to a Low E due the hole being blocked?
    – user54267
    Commented Nov 14, 2018 at 3:42
  • @Detmondyou The point is that it is possible to force not only the second but even higher harmonics by adjusting embouchure and airflow, without using the octave key or the "split fingerings" in the top octave. In fact, one of my teachers encouraged an exercise in which you leave the key closed and force each overtone in sequence, to help learn proper embouchure for the base note and the overtones. Commented Nov 14, 2018 at 13:28
  • I play shawm, and the shawm not only does not have octave keys, it doesn't even have a thumbhole. You must play in the upper register (in this case an octave higher) solely by use of embouchure. Thus, it's no surprise that once you get a note going in the upper register of a clarinet, that you can close the register key and the upper register note will still keep going. As has been said, you need to adjust your embouchure as well to "kick" the tone back down. Commented Nov 15, 2018 at 14:35

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