Adobe has lots of tuts, two of which should help.
https://studio.adobe.com/us/tips/main.jsp
Choose, After Effects from the drop down.
Then you need to log on, or register (its easy).
Will get you this tutorial:
“Using music to animate layers”
This tell you how to convert audio to keyframes and with an expression tie audio to scale (or anything else you want)and how to adjust it to make it work the way you want (can be the hard part if you don’t know what to do).
Another tut on one of the 7 Adobe tut pages:
“Go from dark to bright (or bright to dark) by animating the tint effect in Adobe After Effects 6.0.”
Maybe this will help for brightness, tying audio to % tint for brightness, or use another effect for brightness. Levels maybe?