Last year I made a little modification to STS’ harmonic oscillator, adding a cosine output so as to enable the XY oscilloscope shapes covered by Jerobeam Fenderson in one of his oscilloscope music videos. I finally got round to making another modification, this time making it possible for the frequency of each harmonic to be individually tuned instead of adjusting the phase. The perfectly tuned harmonics can be very beautiful but sometimes slight deviations can add a little movement and character to the sound – also visually – see Jerobeam’s video from around 5m30s.

Jerobeam Fenderson’s oscilloscope music, or the works described in the article on the Digital Harmony of Sound and Light that I looked at yesterday, aim at building an art form based on direct correspondences between sound and vision. I got to thinking Strange Continuity: Why our brains don’t explode at film cuts, an Aeon video that takes a look at why out brains process film cuts so easily, despite their recent appearance on the timescale of human evolutionary history. The argument is that film cuts work because they exploit the ways our visual systems have evolved to work – the filtering already in place to deal with the constant blinking and saccades that apparently render us functionally blind for a third of our waking lives without disturbing our sense of a continuous visual experience.

I was thinking of how the continuity of sound provides a complementary sense to help glue all those visual cuts together – and indeed that is often how film soundtracks work, the Aeon video included. Conversely film cuts opened up our acceptance for abrupt musical juxtapositions – Stravinsky for example. The similarity of film and tape and their modern digital (DAW) counterparts in contrast to modular patches that don’t typically include abrupt transitions. In his talk at Basic Electricity in Berlin Rob Hordijk contrasts the tradition of Musique Concrete with the large electronic studios of the 50s – the studios that can be seen as the starting point of modular synthesis.

The @reaktorplayer twitter account provides a seemingly endless stream of fascinating links on music theory and technology. There’s also a reaktorplayer website covering “thoughts, research and experimentation with electronic music, art and photography.” A recent tweet linked to a PDF on the Digital Harmony of Sound and Light that covers, from a slightly different angle, some of the theory that also underlies the oscilloscope music of Jereobeam Fenderson, for example.

The ‘differential dynamics’ illustrated in the article reminded me of Jerobeam’s DC-offset examples and the rose curve patterns – of which there are some nice animations in the Wikipedia article – have some similarities with the figures I was recently playing around with (again following Jerobeam’s example) using the modified STS Harmonium. For interest’s sake, the difference between the harmonium shapes and Lissajous figures is that both signals (should one restrict the number to two) have a sine and a cosine output, whereas with the Lissajous patterns one signal has a sine and the other a cosine phase.

I spent some time today playing around with STS’ Audulus Harmonium. I added a cosine output in order to be able to create the XY oscilloscope shapes that Jerobeam covered in his video, and rearranged the UI so that it would fit slide-over mode on the iPad. That works out quite nicely with the odd harmonics on the left and the even ones on the right. I’ve been using it in conjunction with MC Studio on the iPad, and enjoy being able to view both the regular waveform and the XY view at the same time.

Here’s a little video of how it works:

It’s interesting to note that the changes in phase don’t have any audible effect when listening with headphones but can be heard when listening ‘through the air’ via a pair of loudspeakers.

Earlier this year, inspired by a lecture by Just van Rossum, I took a look at the ways in which one might translate letter shapes to sound and view them on an oscilloscope. Via Oscistudio, the software I used to make those translations, I got to know a little of Jerobeam Fenderson’s oscilloscope music. He recently published the fourth in a series of video tutorials laying out the technical basis of this art form in a clear and accessible way.

STS has again been as productive as ever, this time with an Audulus Harmonium – an additive oscillator in which the volume and phase of the first twelve overtones of a sound can be individually adjusted: The perfect tool for making some oscilloscope music, should one be so inclined.