To say that Jonathan Pryce plays The Fool in Dario Fo's ''Accidental Death of an Anarchist'' is to say all and yet to leave almost everything unsaid. Mr. Pryce is a master of multiple singularity. Rising to the challenges of an absurdly careening script, he presents a stage persona not only split but shredded: Pryce as the complete impostor with calling cards for all his callings , the wild-eyed lunatic, the phony judicial inspector, the mad lab technician from a '30s horror movie, and a close relative of television's Fr. Sarducci of the old ''Saturday Night Live'' - not to mention fleeting Pryce impressions ranging from Stan Laurel to Groucho Marx.
Time's whirligig is nothing to Pryce's whirly gags as he keeps pace with the prankish political fandango adapted for American audiences by Richard Nelson. The Fool's nom de farce, incidentally, is Antonio Antonio. It would be no more than simple justice if his performance won the lank British farceur his second Tony Award.
The Italo-Anglo-American collaboration at the Belasco Theatre takes place in Rome's central police headquarters, scene of an alleged suicide leap by an arrested anarchist (such an incident prompted Mr. Fo's play). After dealing with an oafish sergeant, The Fool confounds confusion with a masquerade which begins when, as a self-avowed special investigator, he undertakes to help the cops improve their cover-up story. ''Your version of the truth,'' he admonishes the corrupt minions, ''besides being moronic, lacks any human interest.'' He has them replay the events of the fatal night, an exercise that includes the singing , not only of ''The Internationale'' but also the International Ladies' Garment Workers' Union jingle, ''Look for the union la-bel. . . .''
Playing to the audience whenever it suits the author's purpose, The Fool exposes the police as a collection of bumbling bullies. Pratfalls punctuate the left-wing political satire. Call it old-fashioned agitprop with yoks. With the recent American presidential election in mind, The Fool even delivers a stand-up comedy routine comprising a grab bag of Reaganesque quotes. It will delight Democrats while testing the tolerance and good humor of Republicans.
From a nonpartisan standpoint, the trouble with ''Accidental Death of an Anarchist'' may be that its gags go on too long. Even as low-comedy political lampoon, the sketches tend to wear thin. To borrow from Dickens's Mr. Bumble, the law is not only ''a ass, a idiot''; it is a gaggle of buffoons, all pushovers for the subverting prankster.
As previously noted, Mr. Pryce dedicates his formidable comic skills and quick-change artistry to maintaining the pace of the farcical action. The gullible constabulary goon squad is headed by Gerry Bamman (Inspector), Joe Grifasi (Captain), and Raymond Serra (Chief), all of whom serve as willing comic foils. The role of the Sergeant gives Bill Irwin scant opportunity to display his eccentric physical comedy, but Mr. Irwin makes the best of what he is given to do. Patti LuPone brightens up the final scene with a touch of Roman ultra chic as an investigative reporter whose hard-boiled questions evoke only scrambled answers.
''Accidental Death of an Anarchist'' was directed by Douglas C. Wager, with cartoon scenery by Karl Eigsti, costumes by Patricia Zipprodt, and lighting by Allen Lee Hughes. Romance Language. Play By Peter Parnell. Directed by Sheldon Larry.
Back in 1979, Peter Parnell and Sheldon Larry joined forces as author and director, respectively, of ''Sorrows of Stephen,'' a charmingly rueful comedy about an incurable romantic. They have collaborated with less happy results on ''Romance Language,'' the phantasmagoria on display at Playwrights Horizons.
In his wildly free-association plot, Mr. Parnell imagines that Huck Finn (Jon Matthews) persuades Walt Whitman (Al Carmines) to help him search for Tom Sawyer (John Noonan). In the course of their rambling quest, they run into such 19 th-century personages as Louisa May Alcott, Charlotte Cushman, Emily Dickinson, Ralph Waldo Emerson, Henry David Thoreau, and Gen. George Armstrong Custer. (After the Battle of the Little Big Horn, the dead assemble in heaven for a bizarre apocalypse.)
Mr. Parnell writes of his characters: ''Since the sexual frontier is our newest horizon, I have made the characters sexual as well as cultural outlaws.'' Accordingly, several of them engage in sexual encounters of a weird kind.
It may be argued that historical figures are fair game for such cavalier flippancy. In the current climate of celebrity libel suits, however, Mr. Parnell mightn't stand a ghost of a chance even in a limbo court of law.
Under Mr. Larry's direction, the treatment of the material is, by turns, farcical, broadly satirical, and deliberately campy. The cast includes such excellent actors as Frances Conroy, William Converse-Roberts, Cynthia Harris, Valerie Mahaffey, and Philip Pleasants. They cope resolutely with even the play's murky intents and preposterous conceits. The imaginatively designed production has sets by Loren Sherman, costumes by Sheila McLamb, and lighting by Jeff Davis. The musical direction is by Jack Eric Williams, and B. H. Barry staged the fights. In Celebration Play by David Storey. Directed by Lindsay Anderson.
The Manhattan Theatre Club has opened its new season auspiciously with a well-acted British family drama by David Storey. A London success in 1969, ''In Celebration'' inaugurates the MTC's occupancy of the comfortably refurbished downstairs Space at City Center Theater on West 55th Street.
The celebration of the title refers to the 40th wedding anniversary of Mr. and Mrs. Shaw (Robert Symonds and Pauline Flanagan), for which the Shaws' three sons have returned to their North-of-England home. The anniversary happens to fall on the eve of Mrs. Shaw's birthday and one year before the day when Mr. Shaw will have completed 50 years as a coal miner.
The gathering typically prompts reminiscences of former times - of flying kites on the moors that covered the landscape, of churchgoing and Sunday school exercises, and of the once grinding poverty from which the Shaw offspring have escaped. The play is a study in contrasts. Tensions rise as Mr. Storey reveals some traumatizing events of long ago.
Prompting most of these uncomfortable reawakenings is the bitterly cynical Andrew Shaw (Malcolm McDowell), a misfit lawyer-turned-painter who uses his mocking articulateness as an offensive weapon. Andrew's main concern is for his brother Steven (Frank Grimes), a would-be writer who has suddenly abandoned a projected novel after seven years' work. Andrew reserves his particular scorn for brother Colin (John C. Vennema), a successful industrial-relations consultant. Through the interactions in the small household, ''In Celebration'' considers the potentially stiff price for upward mobility in a class society.
Directed by Lindsay Anderson, who staged the original London production and the film version, the Manhattan Theatre Club cast explores perceptively the complex of conflicts that threaten relationships within the Shaw family. Mr. McDowell achieves an exceptional degree of believability as he immerses himself in Andrew's emotional turmoil. The play is also helped by the acting of Mr. Grimes as the intensely troubled Steven and Mr. Vennema as the complacent Colin.