A trumpet becomes a closed tube when the player presses it to the lips; therefore, the instrument only naturally produces every other overtone of the harmonic series. The shape of the bell makes the missing overtones audible. Most notes in the series are slightly out of tune and modern trumpets have slide mechanisms for the first and third valves with which the player can compensate by throwing (extending) or retracting one or both slides, using the left thumb and ring finger for the first and third valve slides respectively. Trumpets can be constructed from other materials, including plastic. Types The most common type is the B trumpet, but A, C, D, E, E, low F, and G trumpets are also available. The C trumpet is most common in American orchestral playing, where it is used alongside the B trumpet. Orchestral trumpet players are adept at transposing music at sight, frequently playing music written for the A, B, D, E, E, or F trumpet on the C trumpet or B trumpet. The smallest trumpets are referred to as piccolo trumpets. The most common models are built to play in both B and A, with separate leadpipes for each key. The tubing in the B piccolo trumpet is one-half the length of that in a standard B trumpet. Piccolo trumpets in G, F and C are also manufactured, but are less common. Many players use a smaller mouthpiece on the piccolo trumpet, which requires a different sound production technique from the B trumpet and can limit endurance. Almost all piccolo trumpets have four valves instead of three—the fourth valve usually lowers the pitch by a fourth, making some lower notes accessible and creating alternate fingerings for certain trills. Maurice André, Håkan Hardenberger, David Mason, and Wynton Marsalis are some well-known trumpet players known for their virtuosity on the piccolo trumpet. Trumpets pitched in the key of low G are also called sopranos, or soprano bugles, after their adaptation from military bugles. Traditionally used in drum and bugle corps, sopranos employ either rotary valves or piston valves. The bass trumpet is at the same pitch as a trombone and is usually played by a trombone player, although its music is written in treble clef. Most bass trumpets are pitched in either C or B. The C bass trumpet sounds an octave lower than written, and the B bass sounds a major ninth (B)