A full dozen years after the death of the sixties’ most imaginative and influential rock guitarist, it’s a wonder that anything at all remains left to release. The Jimi Hendrix Concerts, though, contains material that not only was previously unavailable; it is also among the best in the man’s entire catalog. Featuring 1968–70 performances of “Fire,” “Red House,” “Hey Joe,” and eight other Hendrix classics, the two-LP package sounds as original and timely as anything that issues from today’s artists.