Don't get me wrong. This Forum is always enjoyable, but it's not often more than that. And the moments that achieve genuine liftoff—a superb in-joke in "Comedy Tonight"; also a blissful reprise of "Lovely," the show's romantic duet—make us hunger for more real belly laughs.

It may be that Forum itself is no longer the masterpiece I remembered. Forty-four years (!) after the premiere, Sondheim's music and lyrics have grown in luster. But the Larry Gelbart/Burt Shevelove book, once reckoned the finest ever for a musical, now feels worn; for every two superb jokes, there's at least one clunker. (Forum is a pastiche of ancient Roman comedies, mostly by Plautus. All you really need to know is that Pseudolus, a slave, is promised freedom if he can hook up Hero, the son of his master, Senex, with Philia, a courtesan-to-be, who is promised to Miles Gloriosus, a warrior. Let the games begin.)

In the Arden's plus column, Braithwaite is very nearly the Pseudolus of my dreams, with energy and eclat to burn. He also sings the score, including the famously difficult "Pretty Little Picture," better than anyone I've heard. (Braithwaite is a Philadelphia treasure. Tourists should visit him, along with the Liberty Bell and Pat's King of Steaks.) Richard Ruiz (Hysterium) is maybe even better, and together the two are magnificent. Several other performances are not far behind, including Jeff Coon's splendidly sung Miles Gloriosus and Tom McCarthy's lovable Senex. Alas, the juvenile leads are disappointingly slight of voice and charm, and the often-fine Mary Martello proves miscast as Domina, who must—as the name suggests—dominate. (Paging Hazel Bowers!)

I have similarly mixed feelings about the whole production. Nolen's direction is accomplished and congenial, always keeping things moving (if anything, it's a little too fast-paced). But farce needs ingenious shtick, hairpin turns and vaudeville surprises that are missing here. Ultimately, Nolen's work, like the handsome but inert scenery, doesn't open up the show for wild comic possibilities.

So, for me, Forum was a funny thing—but not a great one. I should report, though, that the audience seemed delighted. And for Ruiz and Braithwaite, it's a terrific evening!

A FUNNY THING HAPPENED ON THE WAY TO THE FORUM

Through June 25, Arden Theatre Co., 40 N. Second St., 215-922-1122, www.ardentheatre.org