WHAT MAKES a singer a singer? Is it a pleasant voice? Or is it intimacy with a song? By the latter standard, actress Geraldine Fitzgerald might be judged a singer, though her weathered voice, drenched with what could kindly be called "character," is hardly a musical instrument. (Then again, Madonna is not much of an actress, either.)

For "Streetsongs," her acclaimed one- woman revue, Fitzgerald has selected an eclectic repertoire of tunes, chosen to fit her definition of streetsongs -- those universal melodies people sing out of doors when depressed or elated. On this live recording of her show, Fitzgerald ruefully notes that people don't do much of that these days.

Simply backed by piano, woodwind and guitar, Fitzgerald sails into a set of tunes familiar and forgotten, including the 2,000- year-old "Danny Boy," a medley of Gershwin's "Swanee" and the Beatles' "She's Leaving Home" (did anyone ever sing that one in the streets?), Noel Coward's "Saturday Night at the Rose and Crown," and a rare English lyric to Piaf's "The Poor People of Paris." Though Fitzgerald's singing is sometimes pained (and, frankly, sometimes painful), her dramatic presence and feelings for the songs can't be denied, and her well- spun anecdotes about each song are fascinating.

The most remarkable moment of "Streetsongs" comes at the end of the record, when Fitzgerald recreates the mood of a London air raid shelter, and leads the audience in singing a rousing, defiant medley of "under-the-street" songs -- including "Who's This Geezer Hitler?," Charlie Chaplin's "Smile" and "Pack Up Your Troubles" -- which recalls the feeling of optimism and pluck in those dark times.

GERALDINE FITZGERALD -- "Streetsongs" (Painted Smiles 1347); appearing at Baird Auditorium (in the National Museum of Natural History) Saturday at 8 p.m. and Sunday at 4:30 p.m.