to distinguish among the instruments in their own product line. The size designation is related to the larger outer branches and not to the bore of the tubing at the valves, though the bore is usually reported in instrument specifications. The quarter system is also not directly related to bell size, though there is typically a correlation. tubas are common in American grade schools for use by young tuba players for whom a full size instrument might be too cumbersome. Though smaller and lighter, they are tuned and keyed identically to full-size tubas of the same pitch, although they usually have 3 rather than 4 or 5 valves. Valves Tubas are made with either piston or rotary valves. Rotary valves, invented by Joseph Riedl, are based on a design included in the original valve patents by Friedrich Blühmel and Heinrich Stölzel in 1818. Červený of Graslitz was the first to use true rotary valves, starting in the 1840s or 1850s. Modern piston valves were developed by François Périnet for the saxhorn family of instruments promoted by Adolphe Sax around the same time. Pistons may either be oriented to point to the top of the instrument (top-action, as pictured in the figure at the top of the article) or out the front of the instrument (front-action or side-action). Piston valves require more maintenance than rotary valves – they require regular oiling to keep them freely operating, while rotary valves are sealed and seldom require oiling. Piston valves are easy to disassemble and re-assemble, while rotary valve disassembly and re-assembly is much more difficult and is generally left to qualified instrument repair persons. Tubas generally have from three to six valves, though some rare exceptions exist. Three-valve tubas are generally the least expensive and are almost exclusively used by amateurs, and the sousaphone (a marching version of a BB tuba) almost always has three valves. Among advanced players, four and five valve tubas are by far the most common choices, with six-valve tubas being relatively rare except among F tubas, which mostly have five or six valves. The valves add tubing to the main tube of the instrument, thus lowering its fundamental pitch. The first valve lowers the pitch by a whole step (two semitones), the second valve by a semitone, and the third valve by three semitones. Used in combination, the valve tubing is too short and the resulting pitch tends