to be sharp. For example, a BB tuba becomes (in effect) an A tuba when the first valve is depressed. The third valve is long enough to lower the pitch of a BB tuba by three semitones, but it is not long enough to lower the pitch of an A tuba by three semitones. Thus, the first and third valves used in combination lower the pitch by something just short of five semitones, and the first three valves used in combination are nearly a quarter tone sharp. The fourth valve is used in place of combinations of the first and third valves, and the second and fourth used in combination are used in place of the first three valves in combination. The fourth valve can be tuned to lower the pitch of the main tube accurately by five semitones, and thus its use corrects the main problem of combinations being too sharp. By using the fourth valve by itself to replace the first and third combination, or the fourth and second valves in place of the first, second and third valve combinations, the notes requiring these fingerings are more in tune. The fourth valve used in combination with, rather than instead of, the first three valves fills in the missing notes in the bottom octave allowing the player to play chromatically down to the fundamental pitch of the instrument. For the reason given in the preceding paragraph some of these notes will tend to be sharp and must by "lipped" into tune by the player. A fifth and sixth valve, if fitted, are used to provide alternative fingering possibilities to improve intonation, and are also used to reach into the low register of the instrument where all the valves will be used in combination to fill the first octave between the fundamental pitch and the next available note on the open tube. The fifth and sixth valves also give the musician the ability to trill more smoothly or to use alternative fingerings for ease of playing. This type of tuba is what is most found in orchestras and wind bands around the world. The bass tuba in F is pitched a fifth above the BB tuba and a fourth above the CC tuba, so it needs additional tubing length beyond that provided by four valves to play securely down to a low F as required in much tuba music. The