Here’s an incredibly cool app: The Shape of a Song. Load the MIDI file of any song into it, and it’ll scan for repeating passages. Then it draws a arch connecting each repetition together. The more passages that repeat — and the more frequently they repeat — the more arches there’ll be. As the designer, Martin Wattenberg, notes:

By using repeated passages as signposts, the diagram illustrates the deep structure of the composition.

This is particularly interesting in light of my blog posting a month ago that asked the question “is music like language?”, and described the work of a physicist who compared the grammar of various types of music. He discovered that “difficult”, atonal music has less repetition in it, which is pretty much what you’d expect — since repetition is partly how a piece of music creates meaning. He singled out Schoenberg’s opening movement from “Three Piano Pieces, Opus 11” as particularly challenging. I’d love to find the MIDI file for that song, load it into this program, and see what patterns it produces — or doesn’t. How many arches would it produce?

By the way, the song illustrated above is “Hold On” by Yes. Yeah, yeah, shut up.