Hi @Taredanna,
You might want to participate in this wish topic:
https://forums.flightsimulator.com/t/ability-to-disable-music/303323
The wishlist is used for requesting new features or changes in MSFS.
You may also submit through Zendesk using the “I want to share my feedback or request a new feature” drop down.
In the mean time, you can mute through Windows sound mixer by app. You’ll just need to remember to unmute it after installation. 