Sarah Gibson, an American pianist and composer whose music combined grace, invention, lyricism and prismatic color, died July 14 at her home in Los Angeles. She was 38.

The cause was colon cancer, said her husband, Aaron Fullerton.

Ms. Gibson’s death came as a shock to the close-knit classical music community, where her work had come in for excited admiration ever since she was in her early 20s. She had been commissioned to write a piece for the Proms series of BBC-sponsored classical music concerts at London’s Royal Albert Hall in August.

She had her new piece, entitled “beyond the beyond,” nearly finished for its world premiere but grew too sick to finish it in time. Instead, the BBC Philharmonic is scheduled to play an earlier composition by Ms. Gibson, “warp & weft” (2021) for large orchestra, on Aug. 8. The world premiere of “beyond the beyond” will happen at a BBC-sponsored concert in 2025, in a version completed by a friend and longtime colleague, the composer and pianist Thomas Kotcheff.

It is expensive to create a work for full orchestra, and most of Ms. Gibson’s early works were for small groups - “Sea Monkey” (2010), “sure baby, mañana” (2016), “Outsider” (2017) and “I prefer living in color” (2017). Ms. Gibson also made a chamber arrangement of the Afro-British pop musician Laura Mvula’s “She.” (Her musical works were often inspired by the works of visual artists, many of them women.)

In 2022, Ms. Gibson was commissioned by the League of American Orchestras to write “to make this mountain taller,” which has already been given its premiere by the Sarasota Orchestra in Florida, with more performances to come.

“To have a commission that gives you a platform like this, with a confirmed premiere and multiple performances, is just huge,” Ms. Gibson told music writer Nancy Malitz. “It’s generally much easier to get your smaller pieces performed, and it’s frankly impractical to write a full orchestra piece if you’re only hoping that it might get played, no matter how much you want to scratch that itch.”

Sarah Elizabeth Gibson was born in Spartanburg, S.C., on May 21, 1986, and grew up in the Atlanta suburb of Roswell. Her father sold retirement plans, and her mother was a homemaker.

She began taking piano lessons at 7 and by her teens was a pianist and principal keyboardist for the Atlanta Symphony Youth Orchestra. Writing in the Atlanta Journal-Constitution, music critic Pierre Ruhe in 2004 praised her six-minute concerto for cello and strings, “Summer’s Breath.” Ms. Gibson, he noted, “creates moments of striking elegance and panache, particularly in her orchestral writing - a serious talent to watch.”

At Indiana University in 2008, she received a double bachelor’s degree in piano performance and music composition. From the University of Southern California, she received a master’s degree (2010) and doctorate (2015) in composition.

In addition to her husband, whom she married in 2014, survivors include their son, Benjamin Fullerton; her parents, Joseph Gibson and the former Beth Medlin of Johns Creek, Ga.; and a brother.

With Kotcheff, Ms. Gibson co-founded the new music piano duo, Hocket, and was a core artist for Piano Spheres, a performing arts organization in Los Angeles that presents concerts of new music.

She served as assistant director for the Los Angeles Philharmonic Composer Fellowship Program and held teaching roles at colleges and conservatories in Southern California.

“Sarah was on a brilliant upward trajectory with her writing and career,” said composer Andrew Norman, a two-time Pulitzer Prize finalist. “She was creating powerful, personal music. ... We are left with a beautifully crafted and deeply felt body of work that will live on.”