This is a set of demos built on top of the Echo Nest API that demonstrate some of the things you can do with the Echo Nest. Current demos are:

The BPM Explorer

The BPM Explorer is a Processing application that will take a song and display a detailed plot of how the tempo changes over the course of the song. You can use these 'click plots' to figure out whether a human or a machine is setting the tempo for a song. A machine-generated tempo is, well, machine like. The BPM for these songs are rock steady and yield a very flat BPM graph - while songs with human metronomes exhibit much more variation in the tempo over time. (I've written more about looking at BPM to detect click tracks and drumming machines here: In search of the click track).