Complex sentence: Despite the last few years of frustration of the Four Lovers, this proved to be the turning point for the group: on a handshake between keyboardist/composer Bob Gaudio and lead singer Frankie Valli, the Four Seasons Partnership was formed.
Split into simpler sentences: Despite the last few years of frustration of the Four Lovers, this proved to be the turning point for the group. Later, on a handshake agreement between keyboardist/composer Bob Gaudio and lead singer Frankie Valli, the Four Seasons Partnership was formed.