The trumpet usually has three valves in its standard orchestral form.
Pressing a valve redirects air through additional tubing, lengthening the instrument’s effective air column and lowering the pitch. Players combine valve positions with changes in lip vibration, called embouchure, to produce different notes. The modern trumpet is commonly pitched in B-flat.
Earlier natural trumpets had no valves and could play only notes available within a harmonic series. Valve technology, developed in the 19th century, made chromatic playing practical and helped establish the modern trumpet’s role in orchestras and bands.
Some trumpets have four valves, especially certain piccolo trumpets, and historical or specialist designs vary. The three-valve model is nevertheless the standard form most associated with orchestral, marching-band, jazz, and popular-music trumpet playing.