A brass instrument is a musical instrument

Musical instrument

A musical instrument is a device created or adapted for the purpose of making musical sounds. In principle, any object that produces sound can serve as a musical instrument—it is through purpose that the object becomes a musical instrument. The history of musical instruments dates back to the...

 whose sound is produced by sympathetic vibration

Sympathetic resonance

Sympathetic resonance is a harmonic phenomenon wherein a formerly passive string or vibratory body responds to external vibrations to which it has a harmonic likeness. The classic example is demonstrated with two similar tuning-forks of which one is mounted on a wooden box. If the other one is...

 of air in a tubular resonator

Resonator

A resonator is a device or system that exhibits resonance or resonant behavior, that is, it naturally oscillates at some frequencies, called its resonant frequencies, with greater amplitude than at others. The oscillations in a resonator can be either electromagnetic or mechanical...

 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

Pitch of brass instruments

thumb|High brass - from the top left: Baroque trumpet in D, modern trumpets in B♭ and D , piccolo trumpet in high B♭, Flugelhorn in B♭; right: cornet in B♭....

: One is alteration of the player's lip tension (or "embouchure

Embouchure

The embouchure is the use of facial muscles and the shaping of the lips to the mouthpiece of woodwind instruments or the mouthpiece of the brass instruments.The word is of French origin and is related to the root bouche , 'mouth'....

"), and another is air flow.