Recording sessions have the mystique of making music history behind closed doors. No matter that the single most famous one in pop culture - the December day in 1956 when Elvis Presley, Johnny Cash, Jerry Lee Lewis, and Carl Perkins, now known as the Million Dollar Quartet, were all in the same Memphis studio - yielded nothing of great musical consequence.

It was lions at play, singing gospel and blues that the public didn't want to hear from them. But who wouldn't have wanted to be a fly on that wall?

No wonder this cultural artifact is the springboard of a jukebox musical, Million Dollar Quartet, which opened Tuesday at the Forrest Theatre, that's everything the original tapes were not - polished, artfully staged, and packaged for mass consumption though the innate funkiness of the music goes missing.

It's an oldies concert with a sketchy plot and quality assurance that comes with a Broadway pedigree. For anyone well-disposed toward 1950s rock-and-roll, the show (running through Dec. 16) is a fun evening that, to its credit, doesn't forget that these are four of the most wildly idiosyncratic talents ever to enjoy mainstream fame.  But anyone who doesn't know the easily obtained original tapes should do themselves a favor and track them down (no pun intended).

The show's conceit: Sam Phillips, the hard-boiled Sun Records founder who is said to have discovered this fantastic four, is the narrator, surfing around plot currents that include the newly discovered Lewis tormenting tough-guy Perkins (then in a hit slump), who is mad at Presley for singing his signature song ("Blue Suede Shoes") on The Ed Sullivan Show. Presley has already moved on to RCA, is back for a visit, and is trying to take Phillips with him. Every song you'd want to hear from that period pops up at one time or another.

Director Eric Schaeffer skillfully guided the actors along that fine line between portrayal and impersonation. Though his voice is suitably deep, David Elkins doesn't come even close to capturing Johnny Cash, but he's an authentic presence, and that counts for everything. Martin Kaye is full of the backwoods weirdness that evolved into Lewis' high-energy outrageousness. As Perkins, Robert Britton Lyons convincingly portrays the arrogance that comes with newfound fame.

Cody Slaughter has the toughest and easiest assignment - Elvis, whose easily imitated physicality has also become as stylized as Kabuki. Slaughter even did The Scarf Ritual when Elvis threw his neck scarves into the audience - all executed deftly. Glimpses of inner character that you get from the others is absent with him. But having seen one of the last concerts by the real Elvis, my sense is that The King was like that, too.