When musician Warren Haynes — of the Allman Brothers, Gov’t Mule and Grateful Dead — announced his short-term intention to move into solo work, Gov’t Mule fans were upset.

It’s not that anyone begrudged Haynes, consistently named one of the top 25 guitarists of all time by Rolling Stone magazine, his chance to pay tribute to the R&B artists that were his first musical love. It’s just that since its 1994 formation, Gov’t Mule has become a musical touchstone. But now, just as Haynes promised, Mule is back and kicking with a new release “The Georgia Bootleg Box.”