By FRANK RICH

''In a Pig's Valise,'' the ''hard-boiled yarn with music'' at the Second Stage, is an homage to detective fiction by a playwright whose affection for Raymond Chandler and Dashiell Hammett may be second only to his love for the sound of his own voice. The playwright is Eric Overmyer, the author of the widely produced ''On the Verge,'' a work of such relentless erudition that its icy intricacies of diction linger long after the play's subject and human mouthpieces have evaporated. ''In a Pig's Valise'' offers more of the same showy verbiage, but, as they say, ''with music.'' Nonetheless, one is most likely to leave the theater humming the similes.

New musicals are so rarely produced, let alone by companies as ambitious as the Second Stage, that the wastefulness of ''In a Pig's Valise'' is dispiriting. The premise, though not original, promises fun. Mr. Overmyer propels his hero, the trench-coated private eye James Taxi (a rumpled Nathan Lane), through every cliche twist known to his pulp genre. As Taxi stalks the Heartbreak Hotel at the corner of Neon and Lonely in the ''kiss-me-deadly night air,'' he encounters femmes fatales, red herrings and unanswered questions that mount up ''like a stack of unpaid utility bills.''

Mr. Overmyer's compulsive, unedited wordplays mount up more precipitously still. Along with similes, ethnic food references and double-entendres, his favorite tic is to tinker idly with familiar phrases: ''a cut and blow-dried case'' or ''I get the driftwood.'' One must do more to parody a literary style that is already, in the hands of its wittiest practitioners, something of a put-on. Mr. Overmyer is clever to a fault, as if he were trying to imitate Tom Stoppard with the aid of a thesaurus. By Act II, the mere mention of the words neon, noir, genre or gumshoe, however linguistically fractured the usage, makes one squirm.

Aside from a funny replay of the slapping scene from ''Chinatown,'' the only amusing riffs are those in which the characters deconstruct their own tale, commenting self-consciously on how vintage detective fiction (and films) rely on the past tense, ''ominous underscoring'' and narrative dissolves. Unfortunately, the plot - something an audience may want even in a mock-detective story - is dismantled by the same academic knowingness. The villains of ''In a Pig's Valise'' are trying to steal American dreams, which leads to an avalanche of secondhand, Leslie Fiedleresque ruminations on the metaphysical, political and erotic implications of national myths perpetrated by the likes of Walt Disney and John Dillinger.

As a musical - or a play with music, or whatever - ''In a Pig's Valise'' seems an uneasy compromise among strong personalities who never found the essential common ground for collaboration. The composer, August Darnell of the band Kid Creole and the Coconuts, is the kind of pop recruit the musical theater desperately needs, but his own style meets the material halfway only in some sultry saxophone solos. While the music and the onstage band are agreeable, the score seems irrelevant to the show's milieu. So do Mr. Overmyer's amateurish lyrics, with their dead words and inevitable rhymes (''I'm a talent scout without a doubt/ I'm the one who's got the clout.'') The director and choreographer, Graciela Daniele, goes her own way as well by evoking the smoky atmosphere of her last theater piece, ''Tango Apasionado,'' without the tangos. Without any drama to propel it, ''In a Pig's Valise'' would have benefited from a galvanizing style. But Ms. Daniele fails to impose a theatrical order that might integrate the seemingly arbitrary musical numbers into the script. Two dancing girls often sashay about for little reason other than a temporary cessation of puns.

Though Mr. Lane is a fine comic actor, he is, as Mr. Overmyer might say, a stalled Taxi - an uncomfortable and unvaried singing detective. The rest of the cast can charitably be described as campy, with the striking exception of Ada Maris, who plays Delores Con Leche, a comic yet sexy lady in red, with more musical-comedy verve than the rest of the company combined. I also enjoyed the usher who deposited me in my seat with the request that I ''laugh really hard, because the critics are here tonight.'' If the response of most of my neighbors was any indication, everybody these days is a critic.

THE MALTESE MAGPIE - IN A PIG'S VALISE, book and lyrics by Eric Overmyer; music by August Darnell; directed and choreographed by Graciela Daniele; set design by Bob Shaw; lighting design by Peggy Eisenhauer; costume design by Jeanne Button; musical direction, Peter Schott; sound design, Gary and Timmy Harris; hair design, Antonio Soddu; production stage manager, Robert Mark Kalfin; stage manager, Paula Gray. Presented by the Second Stage Theater, Robyn Goodman and Carole Rothman, artistic directors. At 2162 Broadway, at 76th Street.

James Taxi...Nathan Lane

Dolores Con Leche...Ada Maris

Zoot Alors and Gut Bucket...Jonathan Freeman

Root Choyce...Thom Sesma

The Bop Op...Reg E. Cathey

Blind Sax...Charlie Lagond

Shrimp Bucket...Michael McCormick

Mustang Sally...Lauren Tom

Dizzy Miss Lizzy...Dian Sorel

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