As young music students know, “every good boy deserves favor” is a mnemonic phrase to remember the treble clef. But the childhood memories of Tom Stoppard and André Previn’s Every Good Boy aren’t the happy-piano-lesson variety. They concern the terrors of totalitarianism that the two artists were lucky enough to escape -- barely.

The protagonists of EGB aren't so lucky. Both are named Alexander Ivanov, and they spend the early 1970s as cellmates in a Leningrad insane asylum. One (called Ivanov) is truly crazy, an amiable fellow who plays the triangle and imagines an orchestra in his head. The other (Alexander) is a political prisoner -- perfectly sane and rational, he has been imprisoned for protesting against the government. A psychiatrist who runs the asylum treats Ivanov with gentle condescension. But Alexander, who has begun a hunger strike, receives the third degree. He is subjected to a series of threats mostly focused on his son Sacha, an inquisitive little boy whom we see locked in ideological combat with his teacher, a dogged party-liner.

EGB is called "a play with music" and it's a genuine hybrid, balancing equally Previn's score and Stoppard's script. The initial idea was Previn's. Then the music director of the London Symphony Orchestra, he envisioned a work that would expand the traditional canon. Working with Stoppard, the subject echoes personal connections (both men are refugees: Previn a German Jew, Stoppard a Czech) and public events (in 1976, Victor Fainberg, a Russian Jew, was imprisoned for protesting the Soviet invasion of Czechoslovakia in an incident that drew international attention). And of course, the metaphor of an orchestra -- a group capable of making beautiful music or cacophonous noise, depending on how it is led -- is apt.

The forces required for EGB are formidable, including a full symphony orchestra and six actors. The logistics are problematic, since a typical concert hall (necessary to accommodate the musical forces) isn't ideally suited to a play -- it's too large, too resonant and not usually equipped with proper lighting. So it's rare to see EGB in performance, despite the intellectual and cultural cache of its origins.

A bigger problem, however, is that the piece is simply undone by its ambitions. EGB lasts just under an hour, but in that time tries to tell a difficult story in both words and music. Previn's score, cleverly sounding like Soviet composer Dmitri Shostakovich, never has the chance to develop fully, since it's constantly interrupted by the play. And Stoppard, famously prone to verbal abundance, must work in relative shorthand. In addition, the playwright seems more comfortable with the ironic banter of the early scenes than the increasing sentiment that comes later. By the end of EGB, the father is speaking in rhymes, the boy is singing in a waiflike, Oliver sort of voice and the audience is growing restless.

Still, much of EGB is remarkably entertaining, and it would be difficult to imagine it better done than here, in a unique collaboration between the Philadelphia Orchestra and the Wilma Theater. Director Jiri Zizka works staging magic with a clever series of triangulated ramps (a lovely metaphor for the musical triangle that Ivanov and young Sacha both play). Late in the action, Zizka brings off a fabulous coup de theatre entrance for a minor character. The actors, led by David Strathairn as Ivanov and Richard Easton as Alexander, are excellent (though Easton is both too old to be Sacha's father and too physically substantial to suggest a hunger striker).

In the hands of the Philadelphia Orchestra and its assistant conductor, Rossen Milanov, EGB's music was superbly realized. Given the shortness of the play, the program opened with the Shostakovich chamber symphony Op. 110a (actually an arrangement by Rudolf Barshai of a string quartet). The piece, by turns mournful and angular, makes a clever curtain-raiser, and the cello-like Verizon Hall suits it perfectly. But to hear authentic Shostakovich before we hear Previn's imitation is to know what the latter aspires to but never quite achieves.