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.