Composer Alex North is enjoying a surprising resurgence on Broadway between his incidental music for “Death of a Salesman” and the prominent use of “Unchained Melody” in “Ghost: The Musical.”It’s even more surprising considering that he’s been dead for more than 20 years. North’s famous film scores include “A Streetcar Named Desire,” “Spartacus” and “Cleopatra.” His work on Broadway, especially with director Elia Kazan and playwright Arthur Miller on “Death of a Salesman” in 1949, eventually led to his move to Hollywood and a career in movies. He received an honorary lifetime achievement Oscar in 1986 and died in 1991. Mike Nichols, who directed the current revival of “Salesman” with Philip Seymour Hoffman as Willy Loman, insisted that North’s music for the original staging be retained. “It’s a great score,” he told Variety. “We’re doing the play in the time in which it was written. So why would you think about ‘updating’ the music, whatever that would mean?” North wrote about 27 minutes of music for four instruments (flute, clarinet, trumpet and cello); it was played live for all 742 performances of the original Broadway run. North revisited the score twice, adapting the original into full orchestral scores for the 1951 film with Fredric March and the 1985 TV film with Dustin Hoffman. Tracking the original scores down, however, was no easy task. They were eventually found among North’s papers at the Library of Congress, copied and sent to New York for a new recording. Unlike the 1949 run, the 2012 version doesn’t have live music; music supervisor Glen Kelly recorded it, and that’s what theatergoers are hearing every night. North’s music, says Nichols, “is the feeling of the family, their secrets and their feelings for each other. It’s a loving family; that’s the saddest thing of all. The other thing that the music knows is that the play actually has a happy ending: Biff is saved and Willy is set free. That’s the secret, at the end of the play, that the music knows all the way through.” “Ghost: The Musical,” based on the 1990 film, has new songs by Dave Stewart and Glen Ballard. But “Unchained Melody” was deemed critical for the show. “The song is so linked to the film that, after only a few bars, people are reminded of ‘Ghost’ and the famous pottery scene,” says producer Colin Ingram. “This has been very useful in radio and TV promotion.” Adds Ballard: “It’s timeless. It’s very simple, very heartfelt; there’s a bittersweetness to it.” “Unchained Melody” originated as the theme for the now-forgotten 1955 film “Unchained” (and received an Oscar nomination as best song). The Righteous Brothers reached No. 4 with the tune in 1965 and No. 13 for the “Ghost”-inspired reissue in 1990. Hy Zaret wrote the lyrics. In “Ghost: The Musical,” the song is quickly established as Sam and Molly’s love song and then resurfaces several times throughout the show, including as an anthem when they are reunited after Sam’s death. (North might have scored a hat trick had the producers of the new staging of “A Streetcar Named Desire” chosen to use North’s jazz-based film score. But composer Terence Blanchard wrote a new score for the play instead.) Dylanna Music, which controls and promotes the North catalog, has issued a new album, “Variations: Unchained Melody,” including reggae, mariachi, Celtic, Hawaiian, jazz and other versions of the classic tune.