This year's Bonnaroo-culminating "Superjam" was curated by the Roots' Ahmir "?uestlove" Thompson, and during the 90-minute show he brought out special guest D'Angelo, the first time the R&B singer has touched an American stage in quite some time. The jam session -- which also featured people like percussionist Frank Knuckles, bassist Pino Palladino, saxophonist Eric Leeds and guitarist Jesse Johnson ...