In pop and traditional music, bass players, which may be upright bass or electric bass, or another instrument, such as bass synth, depending on the style of music, are usually expected to be able to improvise a bassline from a chord chart or learn the song from a recording. In some cases, an arranger or composer may give a bassist a bass part that is fully written out in music notation. In. some arranged music parts, there is a mix of written-out accompaniment and improvisation. For example, in a big band bass part, the introduction and melody ("head") to a tune may have a fully notated bassline, but then for the improvised solos, the arranger may just write out chord symbols (e.g., Bb G7/c min F7), with the expectation that the bassist improvise her own walking bass part.