Coming along in 1976, Tom Petty & the Heartbreakers were part of a movement back to basic, pop-oriented rock & roll that has proven to be the most lasting legacy of a decade otherwise given over to such stylistic flameouts as disco and punk. Never getting too mellow to be mistaken for a sensitive singer/songwriter or rocking too hard to be thought of as a heavy metallurgist, Petty spun out a series of mid-tempo hits patterned on Bob Dylan's classic Blonde on Blonde sound, in which the guitars play off the keyboards while the singer sings lyrics steeped in attitude in a high nasal whine. No wonder the Heartbreakers spent part of the '80s backing Dylan. Petty's only musical development occurred upon his encountering former Electric Light Orchestra leader Jeff Lynne, who helped write and produce his later records, updating them to the Sgt. Pepper's pop sound of 1967. Of course, the consequence of Petty & the Heartbreakers' affection for the music of the mid-'60s was that, in essence, they were a singles band, a fact driven home on the first three CDs or cassettes of this six-CD or cassette box set. Even when abbreviating each of their first nine studio albums to four-to-six cuts (and throwing in a few stray tunes from the live album, the hits album, and a Christmas compilation), the songs break down into the hits and the also-rans. To be fair, there are quite a few of the former, 23 singles-chart entries (22 of them here), in fact, and some of the latter are could-have-beens. And since Petty is more a song maker (or, more precisely, a track cutter) than an album artist, his work is more amenable to compilation. Still, three discs are more than enough, and then come three more discs of rarities and outtakes. The first of these contains non-LP B-sides, most of which are pleasant throwaways (the drummer singing "Psychotic Reaction," etc.), though one, "Trailer," suggests that Petty's failed concept album, Southern Accents, could have been a more of a success if it had been included. The last two discs present early and alternate histories of Petty, as his pre-Heartbreakers group, Mudcrutch, searches for a sound and, later, as he tries out different approaches that never made it onto his regular albums. Some of this material will be of interest to hardcore Petty fans. To justify the length and price of the box, however, there would have to be real lost treasures here, and Tom Petty simply is no Bob Dylan. Not surprisingly, then, Playback is a box set that would have been twice as good at half the size, though it can be thought of as economical in the sense that it can be purchased in lieu of buying Petty's entire 1976-1993 MCA catalog.