The most surprising thing about the New York Philharmonic’s star-studded concert production of Stephen Sondheim’s Company is how unmusical it is. Sure, the orchestra sounds great under the assured conducting of the venerable Paul Gemignani. And it’s a pleasure to hear the lush orchestrations, especially after the recent, pared-down Broadway revival.

But too many of the score’s great songs receive insubstantial treatment, with the ironic result that the evening is most effective in its book scenes, even in the cavernous Avery Fisher Hall.

Still, this Company has its pleasures. The ever youthful Neil Patrick Harris is terrific as Bobby, the 35-year-old bachelor ruminating over commitment issues while observing the relationships of his married friends and juggling several girlfriends. While his voice is not a particularly powerful instrument, he brings a touching emotional sincerity to his numbers, especially the show closer “Being Alive.”

The large ensemble, combining theater veterans (Craig Bierko, Katie Finneran, Aaron Lazar, Patti LuPone and Jim Walton, among others), with a few TV star ringers (Jon Cryer, Christina Hendricks of Mad Men and Stephen Colbert), is a mixed bag.

Not surprisingly, LuPone hits it out of the park with the landmark “Ladies Who Lunch.” And Finneran delivers a delightfully manic “Getting Married Today,” even if she did flub a little on opening night.

On the other hand, Anika Noni Rose fails to convey the requisite intensity of “Another Hundred People”; Hendricks, although endearing as the ditzy flight attendant April, lacks the vocal chops for “Barcelona”; and such group numbers as “You Could Drive a Person Crazy” fail to have the desired impact.

Under the direction of Lonny Price, the disparate ensemble melds together in surprisingly seamless fashion. Although there are times when one is all too aware of the obvious lack of rehearsal time, the evening is a respectable rendition of Sondheim’s classic, even if it lacks the grand musical sweep of such previous New York Philharmonic presentations as Sweeney Todd and My Fair Lady. But that won’t prevent this limited run from being a must-see event for the legions of Sondheim fans.

Avery Fisher Hall, 132 W. 65th St. 212-875-5656. www.nyphil.org.