Complex sentence: These players adopted a more melodic, contrapuntal approach to the instrument; before this, bass players in rock had generally played a conventional timekeeping role within the beat of the song, and within (or underpinning) the song's harmonic or chord structure.
Split into simpler sentences: These players adopted a more melodic, contrapuntal approach to the instrument. Before this, bass players in rock had generally played a conventional timekeeping role within the beat of the song, and within (or underpinning) the song's harmonic or chord structure.