TonnetzViz is an app that visualizes music in real time using the Tonnetz.
The Tonnetz is a diagram representing tonal space. It can be used to visualize harmonic relationships in music. Each node in the diagram corresponds to one of the 12 tones and is connected to 6 adjacent nodes. The ‘neighbours’ of each tone are related to it either by a third (major or minor), or by a perfect fifth, depending on their relative position in the diagram.
One of the interesting properties of the Tonnetz is that any combination of tones (e.g. a chord or a melodic idea) forms a ‘shape’ that is unchanged by transposition. For instance, in the default layout, every major triad is a downward-pointing triangle, and every minor triad is an upward-pointing triangle.
If your browser supports the Web MIDI API, you can use TonnetzViz with any MIDI-enabled instrument. Just connect it to your computer, go to Controls, select the appropriate MIDI port and play. You can also connect TonnetzViz to a software sequencer using a virtual loopback MIDI port.