Covering its subject from 1952 to 1978, from Abba to the Zombies, from doo-opp to the Moog, this 52-hour radio extravaganza treats rock’n’roll as only slightly less significant than the Roman Empire. Produced and peddled by a California program packager, the show features interviews with performers and promoters as well as music by more than 500 artists. In addition to the obligatory and legendary figures like Bill Haley, Fats Domino, the Beatles and Fleetwood Mac, such obscure names as Eddie Cochran, the Rays, Bobby “Boris” Pickett & the Crypt Kickers are represented too. This isn’t the first epic of its kind but it may be the most exhaustive. Followers of specialties like heavy metal or punk rock who want a broader cultural background should be sure to lend their ears. Participating stations will run the program at various times; the first broadcasts begin April 7 in Boston, Washington and L.A. at 6 p.m., with most of the nation tuning in later in the month.