What is the bass in a jazz rhythm sections job?

In a jazz rhythm section the bassist's job is to provide the harmonic and rhythmic foundation for the rest of the group. The bassist achieves this by playing a walking bass line, which can be thought of as the melody in the bass register, or a more static pattern that outlines the chord progression. The bass player usually plays the root of the chord on every beat of a measure, along with notes of chord tones, leading tones, and chromatic passing notes. The bassist's job is to support and complement the other instruments in the rhythm section, particularly the drummer, providing a solid foundation for the rest of the band to play over.

Additionally, the bassist is often responsible for providing a solid backbeat and pulse, which helps to keep the band in time and together. The bassist may also play solos or take turns soloing with the other members of the band, especially in small group settings such as trios or quartets. In these cases, the bassist usually improvises based on the chord progression of the song.