Fantastic Four: First Steps composer drops two MCU bombshells: there's a second F4 soundtrack we "probably won't ever hear" and he's working on a Werewolf by Night sequel

Fantastic Four: First Steps composer Michael Giacchino revealed he completely rewrote the Marvel film's score after not being happy with the initial soundtrack.

"I actually wrote a whole other score for this film that you probably won’t ever hear. I just remember seeing it for the first time with the music and something didn’t feel right," Giacchino told Deadline.

For Giacchino, it appears his work was affected by the much-publicized cuts from the Matt Shakman-directed Fantastic Four, which included a whole sequence involving John Malkovich's Red Ghost not making it into the movie.

"I had built this out based on one version of the movie. When I watched that music against the new version of the movie, I was like, ‘Oh my God, this is not working for me,'" Giacchino recalled.

Giacchino, who has worked on everything from Lost to The Batman, as well as being known for his punny song titles, eventually used a film pickup day to rewrite the score, describing the experience as a product of being in a blockbuster with so many moving parts.

"What we do is a best guess. Everyone is taking their best guess at something and you're not always right," Giacchino said.

The multi-talented Giacchino is also directing a follow-up to MCU special Werewolf by Night, according to Deadline. The composer/director also revealed he is helming an unknown project for Warner Bros. in the near future.

Next up for Marvel is Wonder Man, which hits Disney Plus in January. Spider-Man: Brand New Day swings into cinemas next July.

For more, check out our guide to upcoming Marvel movies and a look back at how to watch the Marvel movies in order.