Broadway's welcome musical break; Little Me Musical comedy by Neil Simon (book), Cy Coleman (music), and Carolyn Leigh (lyrics). Based on the novel by Patrick Dennis. Starring James Coco, Victor Garber, Mary Gordon Murray. Directed by Robert Drivas. Choreographed by Peter Gennaro.

Revived and somewhat revamped, "Little Me" more than wins its welcome in this season of discontent for the Broadway musical. The saga of Belle Poitrine (Mary Gordon Murray), a broad spoof on all those rags-to-riches memoirs, is still as rowdy and about as relevant today as when it first bounced onto the stage nearly 20 years ago. The gaudy shenanigan at the Eugene O'Neill Theater honors the tradition of the musical comedy built around gags, farcical situations, preposterous caricature, and infectious tunes.

Like the original version of the Patrick Dennis novel, Neil Simon's book tells the tale of how Belle Schlumpfert, a voluptuous innocent from the wrong side of the tracks in her Illinois hometown, achieves her dream of ''wealth, culture, and social position.'' But as the reminiscing Belle (Jessica James) of today stridently sings: ''What's here to thrill ya ain't memorabilia.'' Reduced to performing in a sleazy New Jersey night spot, Belle cheerfully recounts in flashbacks her rise and decline.

''Little Me'' revisionism seems to have been occasioned as much by casting as by any other factor. Roles originally played by the inimitable Sid Caesar have for the most part been divided in the revival among Victor Garber (Noble Eggleston, Val du Val, Fred Poitrine, and Noble Junior) and James Coco (Amos Pinchley, Otto Schnitzler, and Prince Cherney). Mr. Coco also impersonates Noble's grand-dame mamma and a millionaire publisher named Worst not in the original cast. Since Mr. Caesar is one of the great comics of our time, it cannot be assumed that his contribution to ''Little Me'' has been approximated. But Mr. Coco plays the sketchlike cartoons with zany intensity while Mr. Garber does amusing variations on the windup juvenile and sings very well indeed.

Miss Murray achieves the rapt innocence - and even a certain touching quality - required of the wide-eyed heroine of this loony tale. Even Miss James's tougher and wiser Belle of the reminiscing years retains good-natured resilience. ''Little Me'' is a show of solid performances - in the principal roles and in such brilliant incidental specialties as Don Correia's gangsterlike ''I've Got Your Number,'' the dazzling solo highlight of Act I. Peter Gennaro's choreography for ''The Rich Kids Rag'' and ''Deep Down Inside'' (re-created from the Bob Fosse original) were among the other numbers that delighted the first-night audience.

''Real Live Girl'' (especially as sung by the male ensemble) remains the loveliest creation of the Coleman-Leigh score. The songs retained from the original also include ''The Other Side of the Tracks,'' ''I Love You,'' ''Boom-Boom,'' and of course the title tune. All relate in one way or another to Belle's dizzying course from her hometown to Chicago; France (in World War I); Monte Carlo; the Atlantic (on the Titanic); Hollywood; and intervening points.

The principal problem presented by these daffy memoirs is that the comic impact of the fatal encounters tends to diminish as the victims multiply. Yet there will be compensation enough in ''Little Me'' for audiences seeking a well-performed, comic, and tuneful show in the Broadway tradition.

''Little Me'' has been energetically directed by Robert Drivas, with humorous sets and costumes by Tony Walton and lighting by Beverly Emmons. Harold J. Wheeler made the orchestrations, and the musical direction is by Donald York.