Someone Analyzed the Chord Progressions of 25,000 Songs
The Hooktheory.com database is where one can go for an analysis of over 25,000 songs. I quote from Amitkohli.com:
These analyses are uploaded by users and allow for all these songs to be analyzed in bulk, as well as individually. One of these ‘all song’ analyses enables users to gather chord progressions on ALL songs (see the analysis file to see how i did it, using the hooktheory API and R). This allowed us to create a Sankey visualization of all chord progressions in the Hooktheory database.
It looks like this.
This obviously needs some explanation. Go here for that.
