With the exception of a brief quartet period between 1978 and 1979 (wherein other members could double on various percussion instruments), Weather Report's instrumentation always included both a drummer and a percussionist. For its first eight years of existence, the group had difficulty finding a permanent drummer, moving through about one drummer per year until Jaco Pastorius helped to recruit Peter Erskine in 1978. Erskine and Omar Hakim were the only drummers who played with Weather Report for more than two years.