Tuba "underblowing" - strange!

[clarnibass]

Hello

A friend of mine is a tuba player and always wondered about something.

He has a CC tuba, and of course he can play low C and continue by overblowing the overtone series. The strange thing is, when he "underblows" the low C it play an even lower F. This has been a mystery to him and I thought someone here might know.

In case it might help, his tuba is (if I remember correct) B&S Perantucci 5/4 CC with rotary valves.

Thanks.

[bassax]

That's called a "false tone".

Brass instruments can often produce a false tone between the fundamental (a CCC on your friends tuba) and the 2:nd partial (a CC) on a big tuba like your friends the false tone would be a FF.

Some tubas have great false tones that could be used instead, sometimes even in favour, of the standard fingerings. On other tubas they just won't center and sounds terrible.