Notes by John Jenkins. All tubas are 'saxhorns' and they are conical in shape, so they start very narrow and then get wider. They are all of similar construction really. The three tubas are of different sizes: high Bb tenor tuba; BBb bass tuba and BBb contrabass tuba.
In common with other brass instruments the sound is produced by buzzing the lips into the mouthpiece. The tuba can sound comical, funereal or many other things, just like any other instrument. People often think of Tubby the Tuba and oom-pah bands as being characteristic of the tuba and indeed it can play in a jocular way but it can also sound very sorrowful, and this is particularly effective in its middle register.
On the continent, they tend to play on the F tuba, and the C tuba, and in this country we tend to play on the Eb and Bb. That is changing a bit; some players are taking on the different instruments. The biggest difference is in the bore size, and so it makes a different sound - a big bore will make a big sound.