The first thing to tell you about the Arden Theatre Company's graceful, intense new production of Sunday in the Park With George is, yes, the well-known tableau at the end of Act 1 works very nicely.

The complicated staging - the act ends in a live representation of pointillist artist Georges Seurat's 1884 masterpiece, Sunday Afternoon on the Island of La Grande Jatte - is true to detail, aided greatly by Rosemarie E. McKelvey's precise late-19th-century costumes. The tableau was also true to detail 16 years ago, when the Arden first produced the Stephen Sondheim musical, staged, as now, by its producing artistic director, Terrence J. Nolen.

But, oh, what a different time that was. The Arden's earlier Sunday in the Park was, by today's standards, from the textbook of purism - which is to say, pre-digital. The last decade or so has thrust multimedia onto stages that can afford it. It's also brought a singular creator of theatrical effects, Jorge Cousineau, to Philadelphia's burgeoning theater industry. Sunday in the Park is a milestone - Cousineau's 40th Arden show, a production he and Nolen co-conceived.

The show itself is a flawed 1984 musical that displays Sondheim's brilliance; his spare but rich music and lyrics mirror Seurat's pointillism and are often dissonant, a happy challenge for an audience.

The first act looks at an obsessive Seurat (the robust-voiced, astute actor Jeffrey Coon) who shuts out the world, including his lady friend (Kristine Fraelich), to labor over his painting - garden-variety Parisians strolling on a warm Sunday. Sondheim and James Lapine, who wrote the show's book, supplied these Parisians with identities; along with Seurat, they are the act's characters.

Move a century forward for Act 2, with George, a modern American artist and Seurat's great-grandson. (Coon portrays him; the other contemporary characters are played by the first-act cast.) George's electronic art is old-hat for him, but he's museum-world approved. By now, art is big money, museum bureaucrats, and critics. Soaring spirits and all that? Coincidental.

This second act has always seemed an add-on, like leaves on an expandable table, or worse, New Jersey on a Pennsylvania map. But special-effects artists and directors of late have been making it a showcase for Sondheim's work and for modern staging. Cousineau and Nolen's mesmerizing Act 2 is stronger than the first - a recent high-digital Broadway revival has nothing over the Arden, the region's premier Sondheim producer. In one particular bowl-over, Coon's contemporary George exits the stage action to sing to us - and several electronic Georges move in.

How strange, then, with all that inventive juice backing a fine cast, that the actors are severely underamplified. Except for Coon, they can be overwhelmed by Eric Ebbenga's excellent musicians, playing the original full Broadway orchestrations - which Sondheim himself encouraged, writing to support a $110,000 grant the Pew bestowed.

The orchestra's not loud, the actors just need a boost; at times they seem to be singing to be heard, not acting in song. Even their dialogue sometimes dissipates. "The challenge," Seurat tells us, is to "bring order to the whole." And maybe a couple of mikes.

Sunday in the Park With George

Through July 4 at Arden Theatre Co., 40 N. Second St. Tickets: $29 to $48. Information: 215-922-1122 or www.ardentheatre.org.EndText

Contact staff writer Howard Shapiro at 215-854-5727 or hshapiro@phillynews.com.