Bass Tuba, brief description
“The tuba is currently used in four tunings: the bass tuba in F and Eb, and the contrabass tuba in C and Bb. In Austrian and French orchestras tubas in F and Bb are used, the contrabass tuba in Bb being found primarily in opera orchestras. In some regions of Germany and in Scandinavia, the United Kingdom and the USA the C tuba with four valves is common as a kind of all-round instrument: it is played not only in the orchestra but also in chamber music and as a solo instrument.”