https://wistia.com/blog/composing-music-for-video
I found this website to be helpful with getting into the right mindset to write music that wasn’t for my own personal enjoyment. It helped me to realise that the right music for the film needed to fit the general atmosphere of the story line.
By this time I had already watched through the film at least 15 times, because of the other aspects we were creating, and from this I had been able to work out that the main direction the film was going for was deception, so I wanted the music to be deceptive too, mixing together two emotions that wouldn’t usually be found together to create an uneasy track.
The main challenge in creating my own brief for the music was that I had very little direction from the director or producer. Before I created the tracks I was told that they wanted something “atmospheric” and “tense”. After showing the team the tracks for the first time I was asked to change one of the tracks to “something more different” and so created a different track using different synths while keeping to the same uneasy feel of the film.
https://music.tutsplus.com/tutorials/using-ambient-techniques-for-composing–audio-4017
I found the introduction and first section of this post to be very useful to creating music that was designed to be in the background of the film. The main limitation I set myself for the music was to not distract at all from the plot and visual of the film, but rather to add to it. To do that I limited myself to creating my music using a maximum of 3-4 tracks for layering, this ensured that I would create music that was thin enough that it wouldn’t overpower the rest of the audio components of the film while also giving me an inspiration to only include music that would benefit the film rather that just going for the most fancy tracks that I could create.