A brass instrument is a musical instrument that produces sound by sympathetic vibration of air in a tubular resonator in sympathy with the vibration of the player's lips. Brass instruments are also called labrosones, literally meaning lip-vibrated instruments.
There are several factors involved in producing different pitches on a brass instrument. Slides, valves, crooks, or keys are used to change vibratory length of tubing, thus changing the available harmonic series, while the player's embouch...
Read more: Wikipedia