Complex sentence: Jeffes and cellist co-founder Helen Liebmann were core members throughout its life and a number of other musicians joined as the band grew and developed, many of whom appear on the PCO's six studio albums.
Split into simpler sentences: Jeffes and cellist co-founder Helen Liebmann were core members throughout its life. A number of other musicians joined the collective as the band grew and developed, many of whom appear on the PCO's six studio albums.