A brass band is composed primarily or entirely of musicians playing brass instruments, such as trumpets, horns, cornets, and trombones. Many brass bands also include percussion instruments, and a few even include woodwind instruments, such as clarinets and saxophones, but must instruments in a brass band are brass instruments. While different bands can vary in many ways, most tend to keep a specific number of each of the types of instruments in a brass band. The particular distribution of different instruments in a brass band tends to vary based on the band's musical style and on the availability and skill of players.
The bass line in brass bands is generally played by tubas tuned to E flat or B flat, or a mix of each. The nature of the bass line varies based on the music style, but it is common for tubas in brass bands to play "walking bass lines," as in jazz. Musicians use such instruments in a brass band to replace the bass instruments, such as bass guitar or bass drums, that would be used in more traditional concert or jazz bands. These instruments are usually used to provide the basic beat that sets the tempo that the rest of the band follows.
Instruments such as trumpets, cornets, and other types of horns play the melody and harmonies over the bass line provided by the tubas. In many brass bands, there is a "principal" or "first" cornet or trumpet that plays the main melody while the others play harmonies. These instruments are often used for improvisation, particularly in brass bands with a jazz-based style. In such cases, the bass line generally remains to provide rhythm while a solo cornet, trumpet, or trombone player improvises a solo. The lengths of such improvised segments vary, but they often come somewhere in the middle of a musical piece, and the melody resumes when the improvised section finishes.
There are many other instruments in a brass band that are used to add balance and richness to those primarily involved in rhythm and melody. Many brass bands actually include percussion sections to contribute to the rhythm sections. Other common brass instruments in a brass band include the flugelhorn, baritone, euphonium, and tenor horn. Some of these instruments are used to add to the melody, others provide harmonies, and still others are used to "blend" the sounds of more prominent instruments with drastically differing sounds.