Homey comedy about WWII experiences of an English family; And a Nightingale Sang . . .Comedy by C. P. Taylor. Directed by Terry Kinney.

After remaining dark for the past two seasons, both of Lincoln Center's drama houses have been relighted within the same month. First came Peter Brook's incendiary ''La Tragedie de Carmen'' to the Vivian Beaumont Theater. Next, a warmhearted British comedy with a World War II background reopened the pleasant little Mitzi E. Newhouse. Result: a gain all round for the theatrical community.

The late C. P. Taylor's ''And a Nightingale Sang . . . ,'' with its humane comedy and honest sentiment, is a treasure of a play. Using pop songs of the period to provide a musical framework, Taylor tells in six scenes what happened to a North-of-England family during the years from 1939 to 1945. ''And a Nightingale Sang . . .'' is a homely play in the original sense of the word. It is a caring and observant writer's simple and unpretentious look at the everyday lives of plain people. Their dramas are important because of the attention that is paid. The play's richness springs from Taylor's concern with the human denominator, the nitty-gritty of Britain's finest hour.

In the central role of Helen Stott, a plain girl who walks with a slight limp , Joan Allen serves the bittersweet comedy as narrator and protagonist. Through Helen, the spectator is introduced to her piano-playing father, George Stott (John Carpenter), a shipyard worker; her fanatically Roman Catholic mother (Beverly May); her indecisive sister, Joyce (Moira McCanna Harris); and the peppery grandfather (Robert Cornthwaite), who spends six months of the year with the Stotts. Through Joyce's soldier fiance Eric (Francis Guinan), Helen meets a fellow serviceman named Norman (Peter Friedman), who, as she says, changes her life.

With various degrees of resourcefulness and courage, the Stotts face up to the dangers and deprivations of a target city in a country at war. As sirens wail, threatened air raids are followed by the real thing. Granddad trades his banjo for a baby's gas mask to protect his pet cat. The Stotts await word of Eric and Norman after Dunkirk. They build their own air-raid shelter. George becomes block warden and is wounded while on duty. Between separations, Helen falls in love with Norman and discovers the self-liberation that will outlast the painful end of a wartime affair.

Miss Allen, who created the role of Helen in the American premiere of the play at Chicago's Steppenwold Theater, is giving a performance as true as it is touching. Unselfconscious and objective, her Helen reviews the Stotts' wartime saga with candor, humor, and affection. The honesty of characterization distinguishes the performance as a whole - an achievement undoubtedly attributable in no small part to the fact that director Terry Kinney also staged ''And a Nightingale Sang . . .'' at Steppenwolf and for the Hartford Stage Company. The production at the Newhouse has been admirably designed by David Jenkins (scenery), Jess Goldstein (costumes), Kevin Rigdon (lighting), and David Budries (sound).