Though the Philadelphia Singers were never about to depart quietly in this, their final season, their East Coast premiere of the Jake Heggie choral opera The Radio Hour has turned out to be far more than anybody bargained for.

"It is an opera," notes Heggie, even though the main character - a woman on the verge of suicide - never speaks. The chorus is split in two, one exploring the contents of the protagonist's head and the other depicting the advice she's getting from . . . could it really be the radio?

The Radio Hour will be paired with Gian Carlo Menotti's 1956 The Unicorn, the Gorgon, and the Manticore in two performances titled "Myth, Magic, and Music" this weekend at Temple University. The Heggie piece is semi-staged, with sets and a chorus that must be quick on its feet. This time, the silent actress will be a dancer.

"It's the dream logic of a woman . . . deciding if she's going to sink into depression or come out the other side," said director/choreographer Sean Curran, who held a special rehearsal during which the chorus tossed roses at dancer Elizabeth Coker. "The piece itself is a strange hybrid. I don't know of any choral opera where the one chorus . . . is the furniture in her apartment telling her to do things."

And surely no choral work has ever had singers declaiming such comic epithets as "Up yours!"

"The radio chorus, in some respects, becomes her therapist," says longtime Philadelphia Singers music director David Hayes. "It asks, 'Why are you letting these things get into your life, like that jerk who returned your letter unopened and didn't even read it?' You're privy to someone talking to themselves."

The music asks the chorus to imitate jazz instruments and use body percussion - finger snapping and more complex effects. Though the Philadelphia Singers haven't memorized the entire piece - as did the Pacific Chorale of Santa Ana, which premiered The Radio Hour in May - many of the singers also work for Opera Philadelphia and bring with them years of stage savvy. With Curran, they need it. "I'm asking them to be triple threats. . . . It's a real negotiation."

"It feels very freeing," Hayes said of doing such an unusual piece when the group is about to disband. "Nobody is freaking out. There's no sense that the fiscal health of the organization depends on this. We're just kind of doing it."

Composer Heggie and librettist Gene Scheer, who created the hit opera version of Moby-Dick, long wanted to create a choral work that would require something beyond the usual stand-and-sing presentation - a more ambitious follow-up to Heggie's previous Pacific Chorale work, a collaboration with Sister Helen Prejean (the real-life nun in Dead Man Walking) called Seeking Higher Ground.

After much trial and error, what resulted was something like the Kurt Weill musical about psychoanalysis, Lady in the Dark, even though Heggie was thinking more along the lines of Alice in Wonderland and Ravel's L'Enfant et les Sortileges, in which inanimate household objects suddenly come to life.

The idea of replacing the silent actress with a dancer came, surprisingly, from the Philadelphia Singers side. Director/choreographer Curran, who has experience staging more conventional opera, was hired to make that happen, and it works so well it's surprising nobody had the idea before.

"There's something about it that makes sense to me . . . though I'm not thinking in terms of an Agnes DeMille dream ballet," said Curran. "It's just abstract movement strung together and made to fit with the music. It's a way for Nora [the protagonist] to be in . . . a kinetic emotional state."

Some creators might oppose such an innovation; for decades, West Side Story couldn't be presented without a facsimile of Jerome Robbins' choreography. But Heggie doesn't see it that way. "Any piece that's worth its salt has to be open to different interpretations and perspectives," he said. "So I'm excited to know what happens."

Because The Radio Hour is less than hour long, other choruses in the commissioning consortium (which includes the Philadelphia Singers) have programmed music that trades on the idea of 1940s radio. Hayes, however, chose the Menotti piece, whose narrative is spread over 12 madrigals encompassing the various stages in the life of a poet who keeps mythical creatures as pets.

Though the Philadelphia Singers has one more concert in May, the fact that the group is winding down with The Radio Hour has special poignancy for San Francisco-based Heggie. "What an honor that they will go out with this piece, which is ultimately very optimistic, about how we can change and transform our lives through connection and community - at any age."

And who knows whether this is really the end for the Philadelphia Singers. Rumors abound about something springing up in its place. Hayes knows of no definite plans but notes that "nature abhors a vacuum. I can't imagine that nothing will arise afterwards."

MUSIC

The Philadelphia Singers

7:30 p.m. Friday and Saturday at the Temple Performing Arts Centre, 1837 N. Broad St.

Tickets: $10-$40.

Information: 215-751-9494 or www.philadelphiasingers.orgEndText