Broadway's welcome musical break; The Curse of an Aching Heart Comedy by William Alfred. Starring Faye Dunaway. Directed by Gerald Gutierrez.

A fragmentary comedy about a forlorn life has brought screen star Faye Dunaway back to a New York stage for the first time in 16 years. ''The Curse of an Aching Heart,'' at the Little Theater, reunites Miss Dunaway professionally with William Alfred, in whose political drama ''Hogan's Goat'' the actress gave the performance that led to her film career.

Moviedom's gain has clearly been the theater's loss. Miss Dunaway gives a performance of warmth, beauty, and spirit as a Brooklyn Irish-American orphan who faces successive tribulations with courage and gallantry. In the course of episodic vignettes stretching from 1923 to 1942 the vigorously independent-minded Frances Walsh (nee Duffy) advances from teen-ager to matron, with a teen-age son of her own. Beginning as a spunky roller-skating schoolgirl, rapt over her first love letter, Miss Dunaway presents the five ages of Frances with true conviction. Alone onstage for the 1942 prologue and conclusion, a maturely philosophical Frances can say ''Yes!'' to life.

In its method of construction, Alfred's memory play makes heavy demands on its star and, to a lesser extent, on several of the other players. Key dramatic developments tend to take place offstage. Motivations are left obscure. At times , the story switches course abruptly. Some characters, like Frances's alcoholic husband (Terrance O'Quinn), simply evaporate or disappear for long years and plot stretches.

Frances herself endures a series of romantic disappointments before finally marrying her childhood crush - who unfortunately turns out to be the wrong man. Alfred's gift for mingling a certain lyricism with the jargon of bygone days (''You ain't just whistlin' 'Dixie,' '' ''Put another record on,'' ''Apple Sauce!'' ''I got your number,'' etc.) enhances the flavor of ''The Curse of an Aching Heart.'' So does his rapport with the Irish Catholic background and related ethnic milieu of his characters.

Such writing and characterization spur histrionic relish. In the production staged by Gerald Gutierrez, the relish is shared by Audrie Neenan in a winningly comic performance as Frances' lifelong friend and by a cast that includes Jon Polito, Colin Stinton, Paul McCrane, Kurt Knudson, Francine Beers, and Raphael Sbarge. One of the play's funniest and most farcical scenes begins with the couple played by Miss Neenan and Mr. Polito serenading Frances and her husband-to-be. Claibe Richardson composed the incidental music.

''The Curse of an Aching Heart'' has been elaborately designed by John Lee Beatty. Visual pleasures include watching an imitation Brooklyn Rapid Transit trolley circumnavigate the multilevel, multistaired setting as it takes on and discharges commuting Brooklynites. The show has been attractively costumed by Nancy Potts and well lighted by Dennis Parichy.

It is good to have Miss Dunaway back in the theater again. One wishes only that she had arrived in a vehicle as sturdy as that Brooklyn streetcar.