I was getting a 500 error on a post of mine utilizing the <audio> shortcode after recently upgrading to WP 3.7.1 and I tried a few things mentioned in some other posts on the same topic and got things working.
I first disabled the JetPack plugin and the 500 error went away, but when going to that same post I would just get a blank page.
After reading the arcicle at the link at the bottom about audio now being part of the core, I changed from using the <audio> shortcode to just putting a full URL http://www.site.com/link/to/file.mp3 directly in my post and it works fine now. Hope that helps!
http://make.wordpress.org/core/2013/04/08/audio-video-support-in-core/