Complex sentence: In June, 1973, Keranen re-joined the group and, in September, 1974, they recorded their first single, "Gorilla", which also appeared on the "Beserkley Chartbusters" compilation album.
Split into simpler sentences: In June, 1973, Keranen re-joined the group. In September, 1974, they recorded the song "Gorilla", released as a single and included on the "Beserkley Chartbusters" compilation album.