According to the band director who gave the low brass their first lesson Tuesday evening, the note that most of them play most easily is an F. When my son played, sometimes it would suddenly drop to a B flat, and the band director told him he could start with either the F or the B flat, whichever seemed easier. But what I kept wondering was, why does it go straight from F to B flat? Why not D, E, or C?
I never played a brass instrument before. I played violin for years, and I tried to learn guitar. I could easily understand how the thickness and length of the string determined the pitch of the note. I also played recorder, and while I never gave a lot of thought to the physics of it, it seemed to make sense that the more holes I covered, the lower the notes were. Longer instruments make lower notes.
I never knew how brass instruments worked, though. I knew that the player’s lip position made a difference, though I never quite knew how. Now that Al is playing one, though, and I am trying to learn it also, I am suddenly very interested in understanding how it works.
It didn’t take me long to find a web site that explained about the important role of harmonics, and another that used the term “standing waves,” but I had to keep looking for a while before I found one that explained this in words I could understand. This article (at a site with a number of helpful article on related subjects) explains first what standing waves are. Next it shows (with helpful diagrams) how the significance of the length of the “container” the waves are in.
I’d never really paid much attention the structure of a brass instrument, but now I have learned that they are all basically long tubes. The tubing curves around, sometimes a lot, but essentially each brass instrument is a long brass tube with a mouthpiece at one end and a bell-shaped opening at the other. How long that tube is determines what is the lowest note that can be played.
Without the valves, the other notes that can be played are also limited by the fixed length of the tube. The lips can be shaped to form higher notes, but only those whose waves fit properly into the length of the tube. I don’t know much about music theory, so that’s about as much of it as I understand, but it makes sense now that I go from an F to a B flat, not a C, D, or E.
I also learned how the valves work. Each one is capable of redirecting the air into an additional length of tubing, which adds to the total length available for the air to vibrate in. (From what I’ve read, some brass instruments are made with ascending valves, where using the valve shortens the total length and raises the tone, but these are less common than descending valves.)
So now I understand a bit better how the instrument makes different sounds when I blow into it. Now if I could just make them sound better…