Arthur Edward Johnstone

“ N.Y. Philharmonic Orchestra
The tuba is the double bass of the brass section of the orchestra. It differs essentially from the trumpet in that its tube is conical and not cylindrical—that is to say. it gradually widens from mouthpiece to bell. The tuba is usually provided with four valves, the fourth of which gives the instrument an extended and valuable downward range.
Prior to its introduction into the orchestra by Wagner the tuba was used only in military bands. ”