Posted by Robert Coulter on February 09, 2003 at 18:13:52:
In Reply to: "double" tubas posted by JoeS on February 09, 2003 at 14:43:48:
I completely disagree with the posters definition of a 'double tuba'. By his logic, any tuba is a double tuba. While yes the fourth valve on a F tuba does pitch the instrument in C, pushing down any single or combination of valves changes the pitch of the horn. A true double instrument is like a double french horn. A different set of slides for the 'other' side of the horn. On tubas it would akin to a type of compensating system. For example on a F tuba...
Open "f side" - F
1 - E
2 - Eb
3 - D
Open "c side" - C
1 - Bb
2 - B
3 - A
But here's the rub... The slides on the C side would be longer than those on the F side, and would have to be to play in tune. Because, if you were on the C side, you're playing through a instrument that is approx 4 feet longer, therefore the valve slides must be longer or they will not be in tune. That's the same reason on non-compensating tubas you have to use progressively more and more valve combinations to produce in tune pitches in the low register. It's a matter of scale. The lower you go, the pitches get further and further apart, so you have to bring in more length of tubing to play them.
So.... A true double tuba would have two sets of slides for each valve, one set for the F side, and one set for the C side.
Somehow, I think I just blew my posting limit for the next 17 months.