Re: Re: Compensating Tuba Question


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Posted by Larry Zaidan on August 29, 2001 at 12:04:01:

In Reply to: Re: Compensating Tuba Question posted by New on August 29, 2001 at 10:03:37:

As I understand it, the fundamental concept is that (for example) the amount of tubing you need to add to a tube, the length of a BBb tuba, to lower it 1/2 step (2nd valve), is a set length. The amount of tubing that you need to add to a tube, the length of a euphonium, by 1/2 step (also 2nd valve), is a shorter length (actually, it is exactly half the length of the BBb tuba 2nd valve tubing). Hence the longer the basic tube is, the longer the auxillary tubing needs to be.

If you take it a step further, when you are playing the low F on a BBb tuba (using the 4th valve), you have effectively increased the overall length of the basic tube. If you then want to lower the low F tubing by 1/2 step, you will come up short, because you are trying to use the auxillary 1/2 step tubing that is appropriate for the BBb length of tubing, not an FF length of tubing.

In the same way, each of the individual valves are designed to lower only the OPEN BBb tubing by: 1 whole step, 1/2 step, 1 1/2 steps, and 2 1/2 steps, respectively (on a 4 valve instrument). Hence, as demonstrated above, when you use (any) valves in combination, the resulting note will be sharp, to one degree or another, depending on the specific combination.

The compensating system is comprised of an instrument that has 2 sets of tubing. The first set of tubes function the same as on a regular tuba. The second set, that is activated when the 4th valve is depressed, adds the appropriate lengths of tubing to valves 1,2,& 3, to correct the above problem. It seems that the compensating system is not perfect, but it is good. (In actuallity, it only fixes the individual valves in combination with the 4th valve, but that seems to be close enough, that you can lip the rest).

I hope that this helps!





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