Piano Heatmap Analysis (Part 2)

Published July 19, 2020 on Chandler Swift's Blog

A long time ago, I hacked together a not-quite-working attempt at tracking played keys on a piano. Today, I took another shot at what that attempt might look like with a few more years’ experience in play.

Here’s what I made: chandlerswift.github.io/piano-heatmap/

demo of the keyboard playing the licc

Because WebMIDI isn’t supported by all browsers (with no plans for Firefox support), you’ll need to try this out in a Chromium-based browser. Plug in a keyboard, and start pressing keys! It displays a nice heatmap of what keys you’ve pressed, updated in realtime.

This is a pretty major update from the way I’d done things previously—as a Windows-first user back in the day, finding tools that were interoperable with others was a larger problem then. Now, I’d be able to compose a few tools (probably aseqdump piped to some combination of grep, uniq, and sort1 would get me most of the way there!) and have it just work, but having an easy-to-use cross-platform display option sounded nice, and WebMIDI promised just that2!

SVG seemed to be an easy way to make a simple keyboard display. (In hindsight, I would have likely been able to do a very similar thing with an HTML canvas, but ¯\_(ツ)_/¯!) I didn’t find any SVG keyboard illustrations that I liked, and wound up drawing my own. I started in Inkscape, but Inkscape adds a lot of unnecessary, invisible content when I’m just trying to display rectangles. I didn’t want anything complex, and the SVG spec is quite simple, so I just built the SVG myself, with a python script for tackling the repetitive bits.

Later on while testing, I did answer a question I’ve had open since Part 1: What’s the distribution of notes like in “Für Elise”? Well, here’s a shot at it3, playing from IMSLP’s Breitkopf edition. This represents once through the entire piece, following repeats, etc., as marked, strictly as written without embellishment. Ten internet points to anyone who wants to download a MIDI file from IMSLP and feed it through here (or record it more carefully than I did!):

a heatmap of the notes in für elise

This certainly isn’t a finished product; there’s no “cumulative score” or anything; and I think having “leaderboards” would certainly be a fun way to motivate practice competitively! However, it’s exactly what I set out to do today—an easy way of displaying the data I’d accumulated previously. Now, off to play some music!

  1. github.com/umdacm/robot/issues/13 

  2. Well, mostly! I did have to download Chromium to get it working, since as mentioned above, Firefox doesn’t currently support WebMIDI. Perhaps this will change, but the bug has been open for almost eight years now, and I don’t want it badly enough to do it myself, so here it sits! 

  3. Since my computer and stage piano are in separate rooms, I dragged a Roland PCR-500 onto my desk as a much more portable tool for testing. However, I didn’t bother wiring it up for sound, so I couldn’t actually hear myself play! I have a pretty good sense of what I’m playing, even without sound, but I certainly make fewer mistakes when I have auditory feedback as well!