When the jazz singer Cécile McLorin Salvant was profiled in The New Yorker, Wynton Marsalis described her as the kind of talent who comes along only “once in a generation or two.” Salvant’s work is rooted in jazz—in the tradition of Ella Fitzgerald and Sarah Vaughan and Abbey Lincoln—and she has won three Grammy Awards for Best Jazz Vocal Album. But her interests and her repertoire reach across eras and continents. She studied Baroque music and jazz at conservatory, and performs songs in French, Occitan, and Haitian Kreyòl.  “I think I have the spirit of a kind of a radio D.J. slash curator,” she tells David Remnick. “It’s almost like making a mixtape for someone and only putting deep cuts.” And even when singing the standards, she aims “to find the gems that haven’t been sung and sung and sung over and over again.” During a summer tour, she visited the studio at WNYC to perform “Don’t Rain on My Parade,” made famous by Barbra Streisand; “Can She Excuse My Wrongs,” by John Dowland, the English composer of the Elizabethan era; and “Moon Song,” an original from Salvant’s album “Ghost Song.”