John Mayer is, by any seasoned Deadhead's measure, a real newbie. Already four albums and seven Grammy wins into his career as a radio-friendly pop/rock star, Mayer first "heard" the Grateful Dead in 2011. The song was "Althea," a late-vintage Dead song co-written and sung by the late Jerry Garcia ? and on Pandora Radio, of all things. Smash cut to four years later: Mayer is about to stand in Garcia's shoes, playing lead guitar and singing dozens of songs during a 15-show fall tour billed as Dead & Company.