During the last 22 years, Widespread Panic has gradually hoisted itself up the rungs of the jam-band ladder, playing an improv-heavy brand of Southern rock. In 2002, Widespread's longtime guitarist, Michael Houser, died of pancreatic cancer, and the band has since gone through a handful of guitarists -- until 2006, when Jimmy Herring (Allman Brothers Band/Phil Lesh and Friends) filled the gap. With some time for the band to congeal, and on the heels of a new album, WSP should be more than ready Sunday, April 27, 7 p.m. at the Landmark Theater. $36.50. 646-7000.