Complex sentence: Harrison started out in the 11-piece reggae collective Echo Base who were signed to the same label as UB40 with whom they toured and despite releasing an album the band felt they were going nowhere and separated.
Split into simpler sentences: Harrison started out in the eleven piece reggae collective, Echo Base, who were signed to the same record label as UB40 with whom they toured. Despite releasing an album the band felt they were going nowhere and separated.