schlepporello wrote:Pitch was very bendable on my Buescher and I've also been able to bend on my 187. I'd always assumed it was the ability of the musician which allowed him to bend pitch, not the horn. Then again, maybe it's just me. I've always been able to play wrong notes.
Nope--playing the tuba inovles an oscillator (your lips) and a resonator (your horn). The coupling of the horn to your lips and the interaction between them produces the effect we call "slotting".
Every resonator has associated with it something called Q, or a "figure of merit". Basically, this is the ratio of the amount of energy stored per oscillation to the amount of energy lost. A fluffy down pillow has a Q of zero. A perfect resonator would have a Q of infinity (which is impossible, since some energy must be inevitably lost).
One characteristic of the Q figure is that it also correlates quite nicely with the width of the resonance peak, measured from the low side half-power point to the hgih-side half-power point. In fact,
Q = center frequency/bandwidth
If you want to make a horn slot less well, drill a hole in it, sandpaper the valves down, stuff it with cotton wool or put a few good-sized dents in it--anything that increases losses will degrade the Q.
Is a horn with a high Q a good thing? Not always--the slotting problem can be really annoying if the resonance peaks aren't in tune with the notes you're trying to play. The sound may be lacking in "warmth" as the horn tends to reinforce only selected frequencies. Response may suffer, particularly in things like lip slurs.
Our reaction to a horn with low Q is that it feels "stuffy"--that is, it doesn't return much of the buzzing energy back to our lips.
A peculiar aspect of this is that the tendency to "slot" may change when you go from loud to soft, because the frequency distribution of the sound produced by your lips changes as you change the amplitude of their vibration. So a horn that slots tightly when played fortissimo may not slot very tightly when played piano.
Art Benade's book "Fundamentals of Musical Acoustics" has lots of good stuff on this.
