and B♭, altos in D♭, sopranos in F, piccolos in B♭, basses in G and E♭, and contrabasses in B♭. Types The most frequently encountered types of trombone today are the tenor and bass, though as with many other instrument families such as the clarinet, the trombone has been built in sizes from piccolo to contrabass. Although trombones are usually constructed with a slide to change the pitch, valve trombones instead use the set of three valves common on other brass instruments. Slide trombones Contrabass trombone The contrabass trombone is the lowest trombone, first appearing in BB♭ an octave below the tenor with a double slide. This design was commissioned by Wagner in the 1870s for his Der Ring des Nibelungen opera cycle. Since the late 20th century however, it has largely been supplanted by a less cumbersome single-slide bass-contrabass instrument pitched in 12' F. With two valve attachments to provide the same full range as its predecessor, this design is effectively a modern bass trombone built down a perfect fourth. Although the contrabass has only appeared occasionally in orchestral repertoire and is not a permanent member of the modern orchestra, it has enjoyed a revival in the 21st century, particularly in film and video game soundtracks. Bass trombone Although early instruments were pitched in G, F or E♭ below the tenor trombone, the modern bass trombone is pitched in the same B as the tenor but with a wider bore, a larger bell, and a larger mouthpiece. These features facilitate playing in the lower register of the instrument. Modern bass trombones have valves that allow a fully chromatic range down to the pedal register (B). In Britain, the bass trombone in G was used in orchestras from the mid 19th century and survived into the 1950s, particularly in British brass bands. Tenor trombone The tenor trombone has a fundamental note of B and is usually treated as a non-transposing instrument (see below). Tenor trombones with C as their fundamental note were almost equally popular in the mid-19th century in Britain and France. As the trombone in its simplest form has neither crooks, valves nor keys to lower the pitch by a specific interval, trombonists use seven chromatic slide positions. Each position progressively increases the length of the air column, thus lowering the pitch. Extending the slide from one position to the next lowers the pitch by one semitone. Thus,