Posted by James W on November 14, 2000 at 11:32:25:
In Reply to: 5th valve on a CC posted by uneducated on November 14, 2000 at 09:46:26:
The more valves you press down at any one time the sharper the tuning of your instrument becomes - if you play low C# on a non compensating CC tuba (1,2,3) and don't pull out any slides or lip the note down at all, the tuning will be miles off. The 5th valve is an attempt to get round this by giving alternative, better tuned combinations for some notes. The usual set up is for the fifth valve to play a flat whole step, and can be used to correct the intonation on notes such as low F, which is usually sharp if you play it 1,4 and flat using 1,2,4. It should be fairly well tuned using 4,5. It also allows for an in tune low C# - something simply not possible on a 4 valve without using an alternative technique (eg. false partials or a compensating system). Some tubas have their 5th valve set up to be a 2 step drop (allowing low E to be played 4,5) but they seem to be becoming less common. Basically, although there are standards and conventions, the fifth valve is a device that is intended to improve the intonation of the instrument, and it's precise use and tuning is a personal matter as decided by the player.
James (another one).