Charlotte Sweet

''An All-Music Musical'' by Michael Colby (libretto) and Gerald Jay Markoe (music). Directed by Edward Stone. Choreography by Dennis Dennehy.

''Charlotte Sweet,'' at the Cheryl Crawford Theater in the Westside Arts Center, lampoons 19th-century melodrama in the context of the traditional British music hall of the era. Subtitled ''An All-Music Musical,'' the operetta by Michael Colby (libretto) and Gerald Jay Markoe (music) tells how sweet Charlotte (Mara Beckerman), who was born on Christmas Day, falls into the clutches of Barnaby Bugaboo (Alan Brasington), an unscrupulous impresario, and his wedded partner in crime, Katinka (Sandra Wheeler).

The Bugaboos are bent on exploiting pretty Charlotte, with her coloratura voice, as the new star of their Circus of Voices.Soon she is singing eight shows a day - her trills filling the till, her high register jingling the cash register. To combat her inevitable exhaustion, the beastly Bugaboos begin forcing her to inhale helium from the balloons they stock for the purpose.

Naturally, the monsters don't reckon with Ludlow Ladd Grimble (Christopher Seppe), Charlotte's loyal sweetheart, and her dear old dad (Nicholas Wyman). Disguised respectively as Queen Victoria and a bobby, they . . . but why spoil the surprise ending?

The singing actors directed by Edward Stone outdo themselves - and occasionally overdo their burlesqueries - but they kept the audience with whom I saw ''Charlotte Sweet'' in a state of appreciative good humor and enthusiasm. Miss Beckerman is a quite delectable warbler. Her mildly balmy fellow circus singers include Michael McCormick, Merle Louise, and Polly Pen. Technical, visual, and musical details have been handled with appropriate care. ''Charlotte Sweet'' is a small, good-natured entertainment - just about right for the size of the hall.