“Showtunes” (Nonesuch), the new collection of songs by Magnetic Fields frontman Stephin Merritt, is the long-awaited answer to a question: What would Merritt do if he applied his formidable songwriting talents to the stage? The answer is not as profound as the asking would suggest – if still better than anything else contemporary musical theater has to offer.

For Merritt, doing theater has always seemed more a matter of when than if. His Magnetic Fields albums can scarcely be reviewed without trotting out the likes of Lorenz Hart and Irving Berlin. He’s likened to Cole Porter so often that he recoils at the mention of him. “I’m so sick of being compared to Cole Porter, now I hate Cole Porter,” he told the New York Times. And he has been approached numerous times about adapting the Magnetic Fields’s “69 Love Songs” for the stage.

Merritt finally made the plunge in 2003 with “The Orphan of Zhao,” a collaboration with director Chen Shi-Zheng for the Lincoln Center Festival. Since then, the duo has collaborated twice more, on “Peach Blossom Fan” in 2004 and on “My Life as a Fairy Tale” last year. “Showtunes” collects 26 of the best songs from the three shows, all of them performed by the original cast and chorus members.

The reason Merritt took his time in getting around to musical theater may be that it isn’t the venue for songwriting it once was. He fairly lambastes it on the song “It’s Hard To Be the Emperor” from “Peach Blossom Fan”: “It’s dull to be the emperor, it’s deadly dull in fact / of all the actors in the court, not one of them can act / an early death seems probable, perhaps it’s just as well / with drama in this dreadful state, my life’s a living hell.”

His work here goes some distance to alleviating the “dreadful state” of things, but he also falls victim to it. So low is musical theater’s stock that Merritt can’t bring himself to do a straight, classical-style musical (which would mean joining the ranks of Elton John and Billy Joel, both in the feeble twilights of their careers). Instead, Merritt has chosen projects that are aggressively eccentric, even avant-garde affairs: The first two plays he did were Western adaptations of Chinese operas, and the third was a non-narrative take on the fantasy life of Hans Christian Andersen.

If Merritt doesn’t overcome these self-imposed obstacles entirely, he at least does some interesting things with them. The Chinese operas allow him to indulge his love of exotic instrumentation: He delights in adapting the plunking and trilling of traditional Chinese instruments for country and western and show tune arrangements.

Quite unexpectedly, the combination produces some wonderful pop moments. “Fan Dance Cha-Cha” and “Ukulele Me!” from “Peach Blossom Fan” could easily double as the theme music for a children’s show. (In fact, they bear a striking resemblance to the recent children’s albums of They Might Be Giants.) And “Train Song,” from “The Orphan of Zhao,” is a reeling square-dance tune (with Oriental instruments played like a fiddle and banjo) that’s too fleet of foot to trouble with words – even Merritt’s nimble ones. It’s better than his Magnetic Fields arrangements would suggest.

“My Life as a Fairy Tale” is altogether more sluggish and less appealing. Mostly oboe and accordion, it is full of the sour, off-kilter sounds of the cabaret and Gypsy camp – music “finely tuned to dying elephants and to the shrieks of toppled kings,” to borrow a lyric from the show.

Like the music, the lyrics are a mixed bag. There’s plenty of occasion for Merritt to brandish his deadpan black humor. “Ah the smell of despair / is that blood in my hair? / I don’t care, I don’t care / what a f-ing lovely day,” runs one memorable verse from the villain of “Orphan.” And few others could do what Merritt does here with anthropomorphic exchanges between a top and ball, an inkwell and pen, or a collar and garter: “he tartly starts up repartee, but her retorts are smarter / she will not set a wedding day / the garter and the collar.”

Lines such as these showcase Merritt’s formidable vocabulary and his talent for percussive internal rhymes, but they do not reveal the full flower of his wit.That shows through in flashes – the Little Mermaid is “autovivisected”; the blind concubine Lola Li is “famous for being a little choosy” – but only in flashes. The best evidence of what Merritt might do for the theater stage is still his work for the concert stage.