The best example of that vision and fiery virtuosity is the 1966 album East-West; on the 13-minute title track, the Butterfield band combined elements of John Coltrane, Ravi Shankar, the Yard-birds and the Byrds' "Eight Miles High" into an audacious, spiraling jam. Tales of the group's high-voltage live explorations of "East-West" have circulated for years; the three takes on East-West Live, recorded onstage in clubland low-fi and collated by Butterfield keyboard player Mark Naftalin, confirm the legend. The performances -- one from early 1967 and two from 1966 -- bristle with the excitement of a band sailing headfirst into uncharted waters.

Bloomfield, who died in 1981, is the unquestioned star of the record. Lacing bluesy lines through Eastern-flavored permutations, he sets up a series of rough-hewed melodies that form a road map for the rest of the band, particularly the passionate blowing of Butterfield on harmonica. Bloomfield may not have played with the gutsy finesse of Eric Clapton or the sonic invention of Jimi Hendrix, but he was a bold musician with both facility and imagination.

The 1966 tapes mix the spark of discovery with the hesitancy of the new. By the time of the 1967 recording -- a 28-minute monster recorded just before Bloomfield quit the group to form the Electric Flag -- the Butterfield band had mastered the tune and its potential, adding new motifs in a suitelike form. You can hear the genesis of the jam aesthetic that stretches from the early Allman Brothers Band to Blues Traveler and beyond. One of the finest archival projects of the year, East-West Live fills in a crucial gap in the histories of a great American band, an underappreciated instrumentalist and even rock itself.