Of all the phases of Sam Cooke's brief, incandescent career — from his early gospel stardom to his amazing leap into pop and soul that almost single-handedly shoved black music into the future — none is more tantalizing than the recordings he made during his final days. From 1963 until his murder in 1964, Cooke restlessly experimented with R&B, rock and soul as he groped for the next breakthrough. It would never come, but that slice of Cooke's career, collected here while he was under contract to Abkco Records, hints at what might have lay ahead. The number that is universally recognized as Cooke's artistic peak — "A Change Is Gonna Come," a hauntingly soulful meditation on civil rights and the turbulence of the 1960s (left off a previous Cooke box set because of licensing problems), shows Cooke moving toward the sort of complex, moving protest music that animated Bob Dylan and Marvin Gaye. Amazingly, it may have been only his first step in that direction. Four other songs — "Good Times" and the superb "Shake," "Yeah Man" and "It's Got the Whole World Shakin' " — lead in the direction of brassy, rhythm-heavy soul that wouldn't clearly emerge until a decade later with Tower of Power. For visionary songs like those, Cooke can be forgiven for a few of the more earthbound ballads that use up space here. But for a glimpse of Cooke's last sessions and its hints of things to come, this is an indispensable collection.