The story of the Allman Brothers Band is one of triumph, tragedy, redemption, dissolution, and more redemption. During the early '70s, they were arguably the most influential rock group in America, thanks in no small part to At Fillmore East (a high-water mark for concert albums), that redefined the scope of rock's musical boundaries. Duane Allman and Dickey Betts pioneered the twin-lead guitar sound so prevalent during the decade that continued well into the 21st century. The group placed an emphasis on musicianship, seamlessly melding rock, blues, jazz, and R&B with extended improvisation.