The Hollywood Chamber Orchestra (HCO) is an American orchestra based in Los Angeles, California, and founded in 2015 by musicians Noah Gladstone and Mark Robertson, who are also co-music directors. Its first public performance was on August 8, 2015, at the Colburn School's Zipper Hall. The program consisted of all horn concertos and was presented by the 2015 International Horn Society. Included on the program was the world premiere of Brad Warnaar's horn concerto, conducted by the composer and performed by Andrew Bain, the principal horn player of the Los Angeles Philharmonic. Their first public ticketed concert occurred on December 11, 2015, at the Montalban Theater in Hollywood, featuring Vivaldi's Four Seasons, performed by Los Angeles Philharmonic concertmaster Martin Chalifour. Other soloists appearing over the last 12 months have included violinist Sarah Chang, pianist Molly Morkoski, clarinetist Eddie Daniels, and singers Cindy O'Connor, Tyler Duncan, Eleni Matos, Garth Neustadter. Franchesca Retford, and Holly Sedillos. Subsequent concerts have included Star Trek:The Ultimate Voyage Tour at the Pantages Theatre, conducted by Justin Freer; and the world premiere of the concert version of the documentary film Blackfish at the Montalban Theater, conducted by composer Jeff Beal. On July 24, 2016, the HCO commissioned and premiered seven new works by composers Michael Barry, Chad Cannon, Andy Forsberg, John Kaefer, Brian Langsbard, Susie Benchasil Seiter, and Andrew Morgan Smith.
On September 19, 2016, the HCO recorded composer Joey Newman's score to the short film Hoshino, a Star Wars fan film directed by Stephen Vitale, written by Eric Carrasco, and starring actress Anna Akana. As of February 8, 2017, the short film has over 1,000,000 views on YouTube. On October 28 and 29, 2016, the Hollywood Chamber Orchestra was the featured orchestra, conducted by Anthony Parnther, for Riot Games' online game League of Legends World Championship Event at the Staples Center and LA Live. As of November 15, 2016, these two concert videos on Facebook have a combined 2.7 million views.
On November 11–13, 2016, the HCO was the featured orchestra for the Orange County premiere of Harry Potter and the Sorcerer's Stone, live-to-picture, conducted by Justin Freer and produced by CineConcerts, at the Segerstrom Center for the Arts in Costa Mesa, CA. Pianist Randy Kerber, who recorded for John Williams' original score to the film, joined the orchestra for all four performances, which were attended by approximately 11,000 people over 3 days. On December 17, 2016, the HCO accompanied Andrew Lippa in the world premiere performance of Swan Lake: A New Musical in Concert, composed by Peter Seibert and J. Patrick Lundquist, at the Montalban Theater in Hollywood.