‘The songs are just laundry lists.” It’s “one-third music” that “doesn’t even belong on the same record player” as its contemporaries.

Even the most cursory stroll through any Broadway chat room will unearth statements this damning and worse, and the level of dudgeon spikes dramatically when the show in question has a 4/4 beat. “Passing Strange” and “Spring Awakening” are just two of the recent rock musicals to send commenters into paroxysms of either ecstasy or rage.

The above criticisms have been lobbed at the spiritual granddaddy of these shows, “Hair,” which is receiving a joyous revival in Central Park at the hands of director Diane Paulus and her talented and — with one exception — marvelously well-chosen group of performers. But those gripes came way back in 1968. (Perhaps the record player reference was a tip-off.)

More tellingly, they came not from anonymous snipers but from the era’s reigning icons of musical theater: The first two were uttered by Leonard Bernstein, who walked out of the show, and Richard Rodgers, who said he couldn’t hear much beyond the beat. And Burt Bacharach, whose “Promises, Promises” opened on Broadway the same year with a decidedly more conventional pop score, was (unfavorably) comparing the music to that of Rodgers when he shooed it away from any turntable within earshot.

When is the last time that Stephen Sondheim or Stephen Schwartz or John Kander uttered a syllable of protest about the current crop of rock musicals? Their silence speaks volumes. The battlefield was much wider and more hotly contested in 1968, when Broadway’s biggest tunes could be heard not merely on specialized satellite radio stations but also on the pop charts. (Four different songs from “Hair” made the Top Five. Just imagine what would have happened if the composer Galt MacDermot and the lyricists James Rado and Gerome Ragni had supplied the other two-thirds of the music.) Every critic who hailed “Hair” as the future of musical theater was essentially consigning the Bernsteins and Rodgerses to the past.

Now that Broadway has somewhat begrudgingly found a home for both old and new musicals (the toughest musical ticket on Broadway right now is Rodgers’s “South Pacific”), what to make of the show that made the Great White Way safe for mass full-frontal nudity and songs such as “Hashish” and “Sodomy”? Now that “Hair” is no longer such a succès de scandale, is it still a success?

It is not meant as a slight — well, not much of a slight — to say that “Hair” is a poorly made musical. The idea of proclaiming independence from the intricately crafted entertainments of musical theater’s golden era served as license for Messrs. MacDermot, Rado, and Ragni to flood the stage with literally dozens of songs and a plot that makes “Cats” look Tolstoyan. Most of Act II, typically the part of a play when all the characters have been introduced and things start to actually happen, is given over to a grievously overextended acid trip.

The majority of these songs do nothing to develop plot or character; they are also wonderful pieces of music. There’s “Frank Mills,” a meandering, rhyme-free, irresistible tune in which a minor character sings of a ne’er-do-well who made off with her $2 and her heart. There’s “Good Morning Starshine,” with its nonsensical “early morning singing song,” and “What a Piece of Work Is Man,” a weirdly cadenced but haunting take on Hamlet’s soliloquy (“HOW no-BLE in REA-son”). And don’t forget the title number’s pouty messianism:

My hair like Jesus wore it,

Hallelujah, I adore it.

Hallelujah, Mary loved her son.

Why don’t my mother love me?

This last song has been put in the hands of the two leaders of “the Tribe,” as the chorus is known. They are the Dionysian George Berger (Will Swenson), who lubriciously approaches anyone in the Tribe (or the audience) regardless of gender or age, and the more conflicted Claude Bukowski (Jonathan Groff), who is grappling with whether to burn his draft card. This plot point — virtually the only one in the entire musical — has been given prominent placement in the drawn-out Act 1 finale, one of many few musical sequences that doesn’t benefit from Karole Armitage’s seamless and plausibly ragtag choreography.

With so little narrative, it is essential that the magnetic pull of these two men keep the non-plot moving. Sadly, only Mr. Swenson obliges. Mr. Groff, a compellingly uneasy leading man in “Spring Awakening,” again comes across here as sweet and gentle, with a plaintive tenor voice. Unlike in the previous show, though, he is also utterly sexless. You half-expect to see his mom swing by Washington Square Park to pick him up before dinner. (Milos Forman’s whacked-out 1979 film adaptation, with its dancing police horses and leering Army recruiters, is presumably of limited use to stage directors. However, its reconception of Claude — as an unworldly Oklahoma boy who stumbles onto the Tribe on his way to Vietnam — might have drawn upon Mr. Groff’s empathic skills while avoiding these deficits.)

But this is the only substantial misstep in a night filled with vitality and emotion. (A recent press performance was interrupted by a half-hour of cold rain; rarely has a group of actors — or, for that matter, an audience — seemed to mind less.) And the fourth-wall-shattering antics of Mr. Swenson and many of his costars offer little preparation for the communal thrill of Ms. Paulus’s finale. I have no idea whether the musical-theater community will draw new sustenance from the ramshackle pleasures of “Hair” or cast a slightly patronizing gaze back at its optimism and indignation before finding the next movie or greatest-hits album to ransack. But I do know that Broadway, if it has any sense at all, will find room for young treasures such as Bryce Ryness, Darius Nichols, Mr. Swenson, and the superb Patina Renea Miller in old as well as new shows. May these gifted young men and women let the sunshine in wherever they go.

Until August 31 (Central Park, enter at West 81st Street, 212-539-8750).