As noted in a statement, Sarah Schachner has said that the "increasingly challenging" dynamic with the audio director on the project has played into the decision to depart from the series.
"I am sad to say I can no longer continue to compose music for MWII / Warzone," said Schachner. "Over the past couple of months the working dynamic with the audio director has become increasingly challenging and I don't see any path forward. As of now, I am unsure of the status and release plan for the soundtrack as it's been taken out of my hands."
Schachner further continues, "While I don't have any control over how the music is presented in-game, what will be released on the soundtrack is not my artistic intent in regards to mixing and mastering. Mike Dean was a part of the creative vision for the album as well as mixer Frank Wolf. We have soundtrack masters in hand from Mike which unfortunately you will never get to hear."
To sound off, Schachner acknowledges the work from the full team to create the soundtrack, and even credits some of the musicians that helped bring the score to life, before adding "I feel a responsibility to the fans to remain authentic in my approach with the game and its sound which I have been part of creating for many years."