The quartet consisted of four different, strong voices and played repertoire of carfully choosen "not so well known" standards, original music as well as filmthemes from the 30's & 40's. The members were Charlie, Ernie Watts, Alan Broadbent and four different drummers over the years: Billy Higgins, Lawrence Marble, Paul Motian and Rodney Green. Luckily the band are well represented on recordings: 7 CDs (on Verve) plus a live recording - Charlie Haden "Private collection"(Naim).
In my humble opinion - one of the really classic jazzgroups of recent times. Go and check them out!