A seismic shift has occurred in the film-composer management world.

Former First Artists Management agents Robert Messinger, Rich Jacobellis and Randy Gerston have left to form their own company, Fortress Talent Management.

First Artists was, along with the Gorfaine-Schwartz Agency, Kraft-Engel Management and WME, one of the four agencies representing most of the top film and TV composers in Hollywood.

Vasi Vangelos and his son Alexander Vangelos remain with First Artists, a company the elder Vangelos founded in 2003. Vangelos declined to comment for this story.

First Artists continues to represent David Arnold, Carter Burwell, Craig Armstrong, Rolfe Kent, Javier Navarrete, Vangelis, Ludovic Bource, Andrea Guerra and Aaron Zigman, among others.

Messinger declined to be interviewed but, in a statement, called this “a time of fundamental change in the film, television and music industries.”

Fortress Talent now has Howard Shore, Philip Glass, Clint Mansell, Gustavo Santaolalla, Rachel Portman, Alberto Iglesias, Mychael Danna, Marc Streitenfeld and Laura Karpman, among other clients.

Both agencies are based in Calabasas.

Agency principals declined further comment on the split.