I was testing something out the other day and I enabled RD mode, I noticed the keyboard flickers on the left and right side to indicate system activity.
Then I got the idea, why not use this as a VU meter/pulser.
I'm not sure if this is possible since:
1. The media player is closed source so I'm not sure how the sound can be detected (unless routed from pulseaudio)
2. Can the LEDs be controlled by the user/program? Sure an echo command would work but that wouldn't be the ideal way to do it.

So what I'm asking, is this possible?