1. Drums: The drummer is responsible for providing the band's overall pulse and rhythm. They play the drum kit, which includes instruments such as the bass drum, snare drum, cymbals, and hi-hats.
2. Bass: The bass player is responsible for providing the low end and harmonic foundation of the band. They typically play a double bass or an electric bass guitar.
3. Piano: The pianist provides harmonic accompaniment and often solos. In some cases, a keyboard or synthesizer may be used instead of a piano.
4. Guitar: The guitarist often provides rhythmic and harmonic accompaniment, sometimes also taking on a solo role. In certain jazz styles, the guitar plays a prominent role within the rhythm section.