Combat Music is a pretty simple mod. When you get attacked by a certain number of mobs, it will start playing music. If you run away from or kill those mobs, the music will stop.
The number of mobs required to be attacking you, the sound events used (they have to be registered sound events), and the time it takes for music to stop playing when you're alone are all configurable.
This mod is completely client side.
External resources
Project members
eerussianguy
Owner
Technical information
License
MIT
Client side
required
Server side
unsupported
Project ID