Complex sentence: Allegedly this caused a falling out with Mick Jagger, and Keys only guested on some shows of the 1975 and 1978 tours, missing the 1976 tour, and performing only two tracks on the 1981 tour, on which Ernie Watts was the main sax player.
Split into simpler sentences: Allegedly this caused a falling out with Mick Jagger, and Keys only guested on some shows of the 1975 and 1978 tours, missing the 1976 tour completely. He performed only two tracks on the 1981 tour, on which Ernie Watts was the main sax player.