But if the vibration were a constant value, we wouldn't hear motorboating and warbles and squeaks with different notes. With bass clarinets (where I have most experience with, and where it's very obvious to the player), a low note clearly makes the reed vibrate at a lower frequency than a high one. The shock waves (pardon the unscientific term) travel forth an back, from the reed away down the bore and back to the reed, and the length of the vibrating air column results in different pitches. And it's at this frequency (or a multitude thereof) that a reed vibrates (or feels like doing so).
Think of a mouthpiece with a reed that is a complete mismatch with the instrument. I played with a soprano sax mouthpiece shoved onto a cornet in lieu of its traditional mouthpiece - the results were, while mighty interesting, not musically pleasing.
I find all this extremely interesting.
First, you mention bass clarinet and later mention oboe. I suck at playing oboe, so I won't mention it further
, but I do play saxophones and clarinets: one thing I noticed when playing a friend's Mark VI straight soprano is that sax players blow more
into the mouthpiece rather than
across the reed, like a clarinet player. In other words, if I'm playing a soprano sax like a metal clarinet, my tone is icky (as you can hear in
this example). If I play it like a saxophone, my tone is OK -- but it's better when I play a curved soprano.
In other words, different ways of making the reed vibrate.
However, you mention the bit about using a soprano sax mouthpiece on a cornet (and there is a sax-trumpet mouthpiece, which I mention on another thread). I've also heard of doing the opposite: use a trumpet mouthpiece on a soprano sax. It sounds kinda like ... a soprano sax. I even think there's a recording of someone doing this, somewhere. (Of course, there's also the oft-repeated story that A. Sax got the idea for a saxophone when he stuck a single-reed mouthpiece on an ophicliede, which is a keyed brasswind.)
You can take a sax mouthpiece and turn it around and blow into the barrel or suck air through the mouthpiece and you will generate a sound. You can do different pitches, too and that would definitely be the reed vibrating at different frequencies. As a matter of fact, I think that this is essentially the way a rackett (Renaissance instrument) works.
Tying all this up, that's why I don't think that the reed
has to vibrate at different frequencies to produce a tone. I think it does
only when the player is adjusting to compensate for defects inherent in the instrument's design (i.e. the "motorboating").
Hey! You've got that mouthpiece robot, JBT! It's got a constant embochure and constant airflow. Does it always play in tune? Can you measure a difference in the frequency the reed vibrates?