He wrote back, telling me that he unfortunately didn't know anything about it, but that he'd think about who we might be able to get in touch with. So I send him over my own notes, here's an ugly copy/paste:
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> Before showing a cut of the film to John Williams, Lucas and Hirsch added to the temp track. The director had designed his film as a "silent movie," told primarily through its visuals and music, so great care was taken to obtain the right moods. "We used some stravisky, the flipside of The Rite of Spring," Hirsch remembers. "George said nobody ever uses that side of the record, so we used it for Threepio walking around in the desert. The Jawa music was from the same Stravinsky piece. We used music from Ivanhoe by Rózsa for the main title. George was talking about having a majority of the film set to music."
> "George had listened to a lot of records and done a lot of research, and people had given him records," Burtt says. "He had picked out some material from Dvo?ák's New World Symphony for the end sequence of the great hall and the awards. He had chosen some of Bruckner’s Ninth Symphony for Luke's theme. We slowly built up temporary music tracks and mixed them in with the film, so we had a temporary version of the film with an essentially complete sound effects track and a patchwork music track that highlighted various moments in the picture. At this point Johnny Williams was brought in."
Rinzler, The Making of Star Wars, p246.
> "I was very pleased with the score," Lucas says. "We wanted a very Max Steiner-type of romantic movie score."
Rinzler, The Making of Star Wars, p265.
> MUSICAL NOTES: The rough edit of Star Wars had a temporary track which used pieces of Gustav Holst's The Planets suite, snatches of Alex North's score for Cleopatra (Joseph L Mankiewicz, 1963) and selections from Bernard Hermann's music for Alfred Hitchcock. Whilst these stock tracks helped create the right mood, there was never - as had been suggested since - the possibility of actually releasing the film with such a track. Lucas wanted a rich, orchestral score, something old-fashioned and outdated at the time. He knew it should be reminiscent of Erich Wolfgang Korngold, the multi-award-winning film composer who had scored The Adventures of Robin Hood (Michael Curtz, 1938) and The Sea Hawk (Michael Curtiz, 1940), two of his moders for Star Wars.
Smith, George Lucas, p75
Note: This is unsourced.
> Another Good example is the temp track for Star Wars. This was Gustav Holst's 1917 classical piece The Planets.
Davis, Complete Guide to Film Scoring, p98 (http://books.google.com/books?ei=3RKzTJHzDY7qOaWqoeYJ&ct=result&id=xSkYAQAAIAAJ&dq=%22star+wars%22+temp+track+john+williams&q=star+wars#search_anchor)
Recording Star Wars: https://docs.google.com/viewer?url=http://www.malonedigital.com/starwars.pdf&pli=1