Wanted to share my experience at the first Music Hack Day in Denver:

This is what my team built:  https://www.hackerleague.org/hackathons/music-hack-day-denver-2013/hacks/makemeshake-dot-it

Sorry about there being no audio on the demo.  We attempted to upload the app to Heroku, but experienced problems with the JavaScript text/picture animation.  If you want to take a closer look at the code you can fork the repository: https://github.com/wvmitchell/makemeshakeit  Some audio depends on the Rdio API so it may not work if you’re not logged in to Rdio.
It was an awesome experience.  Here is are some photos https://www.dropbox.com/sc/okr2kt095f4zfxz/jX9vogTO5E
Also take a look at other projects & businesses from this music hackathon (i.e. The Midem Music Machine, The Bonhamizer, Silly Putty, and The Infinite Jukebox).
I learned that it’s always good to have a plan B at hackathons, and that it is essential to use the sponsors APIs.  The Echonest API is sick!!  All kinds of music data broken down in sessions, keys, and beats.
I only slept 2 hours last night, but I’m wide awake thanks to tons of free Perky Jerky, snacks, food, and coffee.  WOOOO!!