I don't know if I'm translating what you said or not. As a close friend of mine says, "I've got a small brain."iiipopes wrote:OK, everybody has answered what a 5th valve does; nobody answered his initial question why a 5th valve whole step tubing is longer than 1st valve whole step tubing.
The fifth valve is longer because as you combine valves, the tubing is increasingly too short. For instance:
You may be able to adjust your first valve slide so that it is "in tune." You can also adjust your second valve slide to be "in tune." Uh oh, when you employ both at the same time, you don't have enough tubing. This commonly leads to tubists pulling the first valve slide on notes with 1&2 combinations.
The more tubing you employ, the sharper it gets (e.g., 1&3 is sharper than 2&3). Everyone is aware that the 1-2-3 valve combination is so sharp that it almost demands the addition of a fourth valve to be played in tune. Still, 4-2 is a bit sharp but we learn to work with it.
When you play low F on a CC tuba you have two options, 1-4 which is not long enough to play the note in tune and 1-2-4 which is too long. ERGO the advent of the 5th valve which is longer that 1st but shorter than the 1&2 combination.
With this longer 5th valve tubing available you can (conceivably) play the chromatics down to the pedal tone, in tune. Or at least it's workable.
This leads to discussions about alternate tuning of the other valves slides. For instance, players from the 1930's through the 50's often pulled the third valve slide so that it played the equivilent of the "common" 2&3 combination. That, in turn lead some to pull the fourth slide to play the equivilent of 1-2-3... but in tune.
I find the 5th valve to be invaluable to good intonation. Mostly below the staff but it gets a lot of usage.
We spent weeks on this in Intonation Inspector School. The most common citation is issued for high school tuba players with their third valve slide pushed all the way in. It's so common we're running public service announcements about it on radio. It has replaced the ad about the 20,000 bassoon fingerings (one of them HAS to be in tune) but that's another topic too.



