Randy Newman, John Hiatt and Steve Goodman are not the world's greatest singers, but they have written some lovely melodies. You may not appreciate just how elegant their tunes can be until you hear them sung by Mollie O'Brien on her latest album, "Big Red Sun." Tim O'Brien's big sister owns one of those remarkable voices that seem to thicken in tone the longer she holds a note. The precision of her phrasing, the smooth flow of her delivery and the sheer beauty of her alto make her one of the best interpretive singers in American pop today.

For she doesn't merely revive old songs, she recasts them completely to fit her own personality. Listen to the way she changes Willie Dixon's "My Babe" into "Little Baby," making it clear that she's at least an equal in the relationship. Listen to the way she makes the bawdy New Orleans beat count as much as the melody on "Eleezah," a song by her keyboardist John Magnie. Listen to the way she draws out the vowels on Lucinda Williams's "Big Red Sun Blues," until the mixture of regret and affection become unmistakable. Listen to the way her soft consonants and leisurely phrasing reinforce the slacker celebration of Newman's "Rollin'." Listen and appreciate.

Appearing with Rosalie Sorrels, Tom Chapin, Robin Batteau, Jack Hardy, Nina Gerber and Crow Johnston Sunday at the Birchmere.

* To hear a free Sound Bite from Mollie O'Brien, call Post-Haste at 202/334-9000 and press 8128. (Prince William residents, call 690-4110.)