Negative Lines – A Call and Response performance with an algorithm


TL;DR version:

I play the green notes on a midi piano. A computer plays the orange notes. We jam. It is a lot of fun.


This was inspired by Jacob Collier’s explanation of negative melody and polarity, a concept originally by Ernst Levy. In this case every melodic note played by me is inverted around the axis between C and G and the polar opposite note is played back by the computer after a 1 second delay. The notes played as input on a midi keyboard are represented using green circles in the accompanying visualization and the computer’s notes are represented in orange. This kind of audio visual work is hugely inspired by the amazing pianist Dan Tepfer and his Natural Machines project.


Technical info:

The audio processing is done in pure data, which reads the stream of incoming midi information, and creates the response stream of midi as explained above. The two streams of midi are then sent into a virtual midi port (used Loop midi to achieve this). This is then in turn voiced by an instrument of our choosing on Ableton which receives both the streams of midi – human and computer.

The visualization is created using P5Js and run on a browser. (Link to unkempt code)

The tree in the center is supposed to represent a physical manifestation of the concept of negative polarity. The green notes grow like the branches of the tree upwards, while the orange notes grow like the roots of the tree downwards in a beautiful form of balance and symmetry.



This also gives room for a lot more possible variety of jamming with intelligent, more nuanced responses to motifs played by a human performer. It is an exciting territory I wish to explore further.

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