At about the time that John Williams was conducting the world premiere of his “Adventures of Han” theme Wednesday night with the Boston Symphony Orchestra, his “Solo: A Star Wars Story” collaborator John Powell was receiving a lifetime achievement award from ASCAP in Beverly Hills.

It was a bit of unplanned East Coast-West Coast synergy for the film, which opens Friday. Yet in another sense, it was also the Hollywood film-music business in microcosm: The iconic American composer unveiling his latest addition to the “Star Wars” canon that helped make him famous, as the British composer who scored “Solo” was being recognized as among the most respected of those currently working in the field.

Both are quiet, unassuming, and very hard-working composers, although of different generations and from very different backgrounds. “Solo,” the second standalone “Star Wars” movie after 2016’s “Rogue One,” had a complex production history – all the more reason to help assure its success by enlisting the original composer of all those well-known themes.

“John Williams’ involvement was actually a huge factor in my wanting to take this gig,” Powell told Variety. “I have such respect – perhaps awe is a better term – for the musical history of this series that being able to have the film-scoring equivalent of Yoda be part of it was a massive incentive, and an obvious advantage that I could not let pass. The actual experience of being allowed to see into John’s process? I couldn’t imagine a greater gift.”

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Powell was signed last summer and began writing some early themes after he finished the animated “Ferdinand” movie last fall. Williams’ involvement began in late December when, after finishing his scores for “The Post” and his eighth “Star Wars” film “The Last Jedi,” he tackled the theme for young Han Solo.

Williams actually wrote several short pieces, and the “Adventures of Han” theme that debuted in Boston (and which opens the soundtrack album) is a combination of two of them. Powell calls them the “Han hero theme” and “Han searching theme” and utilized them throughout his two-hour score for “Solo.”

“Once John had done his demos (recorded in Los Angeles in January), I started to work out where they would go. But there was a lot of other material that we needed as well,” Powell says.

Powell’s own music includes a romantic theme for Han (Alden Ehrenreich) and Qi’ra (Emilia Clarke); a friendship theme for Han and Chewbacca; another for outlaw Beckett (Woody Harrelson) and his gang; a choral piece for the Marauders who upset the gang’s plans; a theme for L3, droid companion to Lando Calrissian (Donald Glover); and a few other minor motifs.

Augmenting the new Williams theme and the multiple Powell themes are various familiar bits from early “Star Wars” scores, including Williams’ “Rebel Fanfare,” associated with the Millennium Falcon; the original “Star Wars” theme, which Powell applied as a “destiny” theme for Han; and action music from both “Star Wars” and “The Empire Strikes Back.”

“I tried to keep in mind the DNA of how John writes, which is flow and polyphony and melody, and of course an incredibly interesting rhythmic use of the orchestra,” says Powell. He recalled visiting Williams and consulting with him via phone: “He was incredibly generous, and very trusting of me.”

Powell recorded the score with a 98-piece orchestra in March at London’s Abbey Road studios, but made a quick side detour to Sofia, Bulgaria, where he recorded a 36-voice Bulgarian women’s choir. He said they offered “an aggressive, exotic sound” for the Marauders of the story, “to feel like a different culture had arrived on the scene.”

He had fun penning a song, which he calls “Chicken in a Pot,” as background lounge music for a scene with Han, Qi’ra, and Dryden Vos (Paul Bettany). Powell wrote lyrics that were translated into Huttese, the strange language invented by sound designer Ben Burtt for the original “Star Wars” trilogy.

Director Ron Howard was “a dream director for a composer,” Powell says. “He is enthusiastic, he is clear, and he’s also very open and expressive about what each scene is about. Overall, he allowed me to experiment, and slowly we worked out what our style was and how the themes needed to behave.”

“It was a very enlightening and maturing experience,” Powell adds with a laugh. “This has taught me a lot about how elegantly John Williams writes. I really loved using his themes in different versions, because they’re so beautifully constructed. It was like doing my master’s degree.”