Audio-Visual Rainbows: Mapping Microtonal Pitch-to-Hue by Amanda Cole

My Love of Rainbows

Some of my favourite rainbow coloured things.

Every since I was a little girl I have had a fascination with the colour spectrum. Starting with organising packets of smarties or textas into rainbow order in my early years, I progressed to knitting, crocheting, painting and collaging rainbows in my teenage years. I have many rainbow colour scheme objects from art museum shops, rainbow clothing, a solar powered crystal rainbow maker and I love Rainbow brand chai. So what I am basically saying is I LOVE RAINBOWS!

24-note to the octave just intonation Cube-Tuning by Amanda Cole mapped onto a tuning lattice.

My Love of Microtonal Tuning

My other main interest is microtonal music composition, which generally involves using notes from the harmonic series to create just intonation or spectral tunings. What I love about using microtones is the infinite palette of notes that are available between the cracks of the 12 notes on the piano. Like the limitless hues of the colour spectrum, pitch is a continuum of infinite notes and intervals.

I love microtonal tuning as you can work with whole number ratios found in the harmonic series. These notes can be heard in overtone singing and as harmonics when when divide a string at its fractional points. Conceptually I see the harmonic series as being connected with nature and the piano tuning as being a person-made tuning without the same mathematical purity. The the volume each individual overtone of a particular instrument gives us its timbre. A flute has louder even overtones and a clarinet has louder odd overtones. A microtonally tuned instrument such as a piano can set off new overtone interactions between played notes that you wouldn’t normal hear, changing the familiar piano timbre.

I also love microtonal intervals that are close in pitch as they can make enharmonic scalic steps and interference beats when played together. Basically, what is not to love about microtonal tuning!

Using Coloured Water to Map Unfamiliar Scales

I started to work with colour and microtonal scales as a postgraduate student when I built a custom made 60-glass Microtonal Glass Harmonica, tuned to two octaves of Harry Partch’s 29-note to the octave just intonation scale. I colour coded six sub-scales with food colouring in the water of each glass. The colours helped the percussionists navigate the unfamiliar scales and made the instrument looked really pretty!

Amanda Cole’s ‘Microtonal Glass Harmonica’. Pieces for this instrument have been performed by Joshua Hill, John Dewhurst, Jeremy Barnett, Kim Moyes, Jared Underwood, Bree Van Reyk and myself.

Mapping Microtonal Pitch to Hue

I then moved onto mapping Partch’s 43-note to the octave just intonation scales to make some audio-visual animations in Max/MSP. I divided the colour spectrum into the same proportions as one octave of the scale to get 43 different colours. I mapped the 256 colour hues to the 1200 cents in an octave using the formula:

Hue = interval in cents from fundamental/1200 x 256

In Max/MSP I was able convert the hue values between 0 and 255 into RGB (red, green, blue) value using the swatch object. I also now had a way to map notes of any microtonal scale to RGB colours and vice versa.

43 RGB colours mapped to the Harry Partch’s 43-note to the octave scale.

Melatonin Shift #3 (from the series Time—Feeling Time 2003–06) by Robert Owen — *Melatonin Shift #3* (from the series *Time—Feeling Time* 2003–06) by Robert Owen

I did experiment with mapping hue-to-pitch using Robert Owen’s ‘Melatonin’ painting as a score. I ‘read’ his painting as columns where the duration of each note was determined by the length of each colour block. My sister Jayne Blake (who did my website logo) did an analysis of each RGB colour in the painting. It was an interesting process but I realised that I wanted to control the musical outcome more. You can listen to the music this painting made on the ‘pieces’ page of my website: Melatonin Shift Audio

Making Light Instruments

My first piece using light and music was ‘Polymetrica’ which was scored for my ‘Programmable Light Metronome’ and percussion quartet. The ‘Programmable Light Metronome’ was made from two strings of Christmas lights that could be programmed through my computer to flash at different tempos. The electronics were made by the father of my percussionist friend John Dewhurst, who was playing in the quartet. Polymetrica explored metric modulations and polyrhythms in music and light.

My next light instrument was made for a recorder duet with coloured light for a concert that was part of the Vivid light festival in Sydney. Recorder players Alana Blackburn and Jo Arnott played an ambient microtonal piece where the frequencies of each note triggered coloured lighting. I used my pitch to RGB hue mapping formula in Max/MSP to convert the live pitches of each instrument into coloured light.

Another light instrument I made was triggered by drums for a piece called ‘Flicker’ that was a one-minute commission for Synergy Percussion’s 40th birthday. In this piece for a quartet of drums, certain light colours were assigned to combinations of players striking notes at the same time. In the excerpt of the score below you can see how blue is mapped to a unison in percussion 2 and 4 and orange is mapped to a unison in percussion 1 & 3. There is a video of this piece here: Flicker Video

Flicker by Amanda Cole for Synergy Percussion. Combinations of unison notes by different players triggered different coloured light. Players 1,2 & 3 = red and players 1 & 4 = yellow.

Colour mapping of RGB Glass Rainbow Maker

RGB Rainbow Glass Maker

The RGB Rainbow Glass Maker instrument was created for the performance of a piece called ‘Bowing Rainbows’ in the Backstage Music series in Sydney in 2019. This piece was also scored for violin and piano strings. The RGB Glass Rainbow Maker has three glasses, tuned to perfect 5ths A (red), G (green) & D (blue), which were chosen as they match three of the open string notes of the violin. Each glass has a contact mic attached that goes into my audio interface and then into my Max/MSP patch on my laptop. The live wine glass notes are used to trigger spectral frequencies of the wine glass notes to create additive synthesis. Food colouring is added to the wine glasses to make a red, green and blue glass that triggers the same colour in light. When two glasses are played at the same time the colours are added together create a new colour. This instrument uses additive light and additive sound synthesis. Last year in the Sydney lockdown I did a one-hour set on this instrument for the online Hibernation Festival. I recently demonstrated this piece for the first composition year students at the Sydney Conservatorium (via Zoom) and managed to do some filming that you can now watch on YouTube.

The next version of this instrument will add percentages of red, green and blue based on the volume of each glass played to create even more RGB colours!

Colours the RGB Rainbow Glass Maker can make : Red, Magenta (red + blue), Blue, Cyan (green + blue), Green and Yellow (red + green). .

Spectral Microtonal Pitch-to-Hue Mapping

I have recently come up with this pitch-to-hue mapping for overtones of the harmonic series. In the diagram below I have mapped harmonics 1-23 and have shown the colour scheme for different scales. This spectral mapping could be extended up the harmonic series to get more colours. I am yet to make a work with this mapping but I think it could work well for a new wine glass piece or an interactive audio-visual vocal composition.