Some jazz duos consist of a singer accompanied by a single piano player. In these duos, the jazz piano player has a challenging task; they have to provide all of the rhythmic and harmonic foundation that would normally be provided by a full rhythm section. A jazz pianist accompanying a singer in a duo needs to play a deep bassline, chords, and fill-in melody lines while the singer is performing. The pianist often improvises an instrumental solo in between vocal melodies.