Because, bottom line, it's still Rodgers and Hart, and it's still musical comedy in its purest, most escapist state. Shakespeare's farce of two sets of identical twins in ancient Ephesus -- an early work and, it is generally conceded, a sloppy one -- is ideal fodder for musical-comedy silliness, what with its confused identities, slapstick slaves, neglected wives, luscious courtesans, and mercenary merchants. Syracuse was the first major Bard-meets-Broadway musical and, as any fan of the team knows, Rodgers and Hart loved a challenge. They were always at their best as innovators, whether liberating the early movie musical from stage conventions (Love Me Tonight) or giving the musical stage its first-ever antihero (Pal Joey).

The Boys from Syracuse opens with a complicated ensemble number spinning yards of exposition into ingeniously witty couplets ("I Had Twins"), and from there it's one beauty after another. Take "Falling in Love With Love": Hart's rueful lyric doesn't believe in love, but Rodgers's ecstatic waltz does, and the tension is still captivating 64 years later. And when Hart dishes up a couplet like "When the search for love becomes a mania / You can take the night boat to Albania" (a sly reference to the prostitutes who worked the old night boat to Albany), you want to dash back to 1938, give the ever-unhappy Hart a hug, and assure him that, yes, he's deeply loved.

The brilliance of the pair shines through at the Roundabout, even if there are times when it seems that meddlesome revisionist hands are trying to obscure it. Two songs from other R&H works have been needlessly interpolated. "You Took Advantage of Me," from the 1928 Present Arms, opens the second act, even though it's connected to nothing. "A Lady Must Live," from America's Sweetheart (1930), is presented as a brothel entertainment; it's similarly irrelevant, and it features the most vulgar musical staging since "My Defenses Are Down" in the Annie Get Your Gun revival. Don Sebesky's new orchestrations are garish and obvious, with yuk-yuk sound effects, and David Loud conducts bizarrely, with tempos that the purist Rodgers would surely have vetoed. Hugh Martin's superb original vocal arrangement of "Sing for Your Supper," a surefire show-stopper, has been scrapped in favor of a lackluster new one. And where is "The Ladies of the Evening," with Hart cracking wise about the cop-hooker dynamic?

Or maybe that's the doing of the aptly named Dilly, who sings sweetly, looks great, and has a comedic sense rare in an ingénue. (This planet could use more daffy sopranos, along with more Rodgers and Hart songs.) Outstanding, too, is the burlesque-savvy DiBuono, nicely partnered by Lee Wilkof's Dromio of Syracuse with his Borscht-Belt timing and lumpy, comic mask of a face. The rest of the cast is generally competent, though there are some curious choices; these two sets of twins don't look remotely identical, which renders the whole story more absurd than it has to be. Lauren Mitchell finds the right mixture of warmth and harpiness in Adriana but she doesn't make "Falling in Love With Love" soar as it should. Jackee Harry's Madam has sassiness but little else, and Chip Zien's Dromio of Ephesus is pallid next to the more instinctively comedic Wilkof.

Scott Ellis directs fitfully; some scenes have the proper comic snap but others seem to be marking time until the next song cue. (Ellis does come up with one superb sight gag, worth watching out for, at the end of "He and She.") Rob Ashford's choreography seems skimpy, especially after all that heavy tapping he contrived for Thoroughly Modern Millie. So does Thomas Lynch's set design, all flats and garden furniture. The costumes, by Martin Pakledinaz, are all over the map, from Vegas sequins to Frederick's of Hollywood nighties to Li'l Abner striped socks and polka dots. Eclecticism can be funny in farce, but here it's just haphazard.

So, it could be argued, is the whole evening. But just as you're about to give up on it, Silver gets off another good one, or another Rodgers melody triumphs over its arrangement, or another Hart lyric elicits a real belly laugh. This may not be anybody's dream production of The Boys from Syracuse, but it will take stronger hands than the Roundabout's to kill so sturdy a musical.