Complex sentence: He was a member of blues-rock outfit, 1984 and later Smile, a band which included guitarist Brian May and drummer Roger Taylor, and which, upon Staffell's departure, hired Freddie Mercury and John Deacon to form the band Queen.
Split into simpler sentences: He was a member of blues-rock outfit 1984 and later Smile, a band which included guitarist Brian May and drummer Roger Taylor. Upon Staffell's departure, Smile were joined by Freddie Mercury and John Deacon to form the band Queen.