Complex sentence: Simba Wanyika continued playing rumba, and was still quite popular when the band split in the late 1970s when rhythm guitarist Omar Shabini took many of the bands musicians and forming Les Wanyika.
Split into simpler sentences: Simba Wanyika continued playing rumba, and was still quite popular when the band split. In the late 1970s, rhythm guitarist Omar Shabini quit the band, taking many of its musicians with him and forming Les Wanyika.