To compensate or not to compensate? That is the question.
Like all brass instruments, the tuba and euphonium have an issue with their lowest notes. Any three-valve B-flat non-transposing instrument will hit its lowest non-pedal note on E (all three valves pushed down). Players and composers wanted extra range, so a fourth valve was added. This valve opens a length of tubing equal to the first and third valve tubes combined. Trombonists have something similar – the F attachment, which is equivalent to putting the slide in sixth position. It’s almost an octave-down key, thanks to the vagaries of the overtone system. For example, E-flat 3 is first valve, and E-flat 2 (one octave lower) is valves 1 and 4.
The problem is that the lower the pitch, the longer the tubing needs to be. At a certain point, notes on the tuba and euphonium are so low that the tubing isn’t long enough. At about D2, you have to finger the note one half-step down from the corresponding fingering up an octave to compensate for the tubing issues. For example, B2 on a euphonium is valves 1, 2 and 3, but pushing 1, 2, 3 and 4 down on a euphonium will generate C2 instead of B1. This means that, in its lowest octaves, the instrument isn’t fully chromatic.
The solution was to create what’s called a compensating system for the horn. In this, whenever the fourth valve is pushed, the airflow is not only redirected through the fourth valve tubing but also through smaller bits of tubing that add the required length to compensate for the half-step issue. This makes the horn fully chromatic over the entire range – but it also adds weight to the horn. Not a lot of weight, but noticeable. The extra metal can also affect the sound somewhat, though a good player can adapt.
Not everyone likes compensating horns, especially if they rarely use the lower register in their playing. Players out there – what is your opinion?