100 Keyboards – fusing music, physics and physical movement into orchestral pandemonium (The MAC until Saturday 19 October) #BIAF19

Over a hundred small battery-operated keyboards radiate out in concentric circles around a small lamp. The artist Asuna tiptoes in his red sock soles through the instruments, turning some on, jamming short lollypop sticks into them to sustain particular notes. The audience sit on cushions, chairs or stand right round the 100 Keyboards orchestra.

At first it’s the same note on the handful of keyboards, before a second and third note emerge, forming a seventh chord. Interdisciplinarity is one of Belfast International Arts Festival’s themes for 2019. Hiroaki Umeda’s Accumulated Layout and Media earlier in the week – another partnership with the Japan-UK Season of Culture – fused together sound, visuals, coding and movement. 100 Keyboards is part physics, part maths, part music, and part dance as the nimble artist continuously circles his one-man orchestra building up the bespoke piece he’s playing.

Each electronic keyboard, playing its relatively pure continuous tone, emits a wave of sound. Yet the positioning of the instruments – most of the time there’s a mirror image keyboard on the other side of the lamp, and sometimes to both sides too – means that these similar waves will overlap, collide and interacting, creating a superimposed Moiré effect.

Sitting on a cushion on The MAC floor, I slowly sway from side to side, my head and as my ears move, certainly tones suddenly stand out from the massively distributed chord, then fade back into the melee.

Asuna only stops to shed another layer of clothing. It’s a sweaty business as he hunches over his musical laboratory playing with sine waves. Sometimes the insertion of a single stick to hold down a key on a keyboard changes the whole soundscape, breaking whatever settled pattern had been in place.

With thirty or forty different models of keyboard in front of him, Asuna reaches to a different place to find the on switch and control the volume. One or two naughtily play a demo tune as soon as they’re switched on before complying with the master’s instruction.

The purity of a seventh chord has long since gone and the controlled cacophony reminds me of a peel of bells, with one clang still decaying when the next bell is struck and cuts through. There’s movement in this sustained chord.

Forty minutes in and what began as quite a quiet and meditative performance is becoming more oppressive. I wonder if I’m hearing the sound of cars driving around north or west Belfast blaring their horns in celebration of the Brexit deal … before remembering that that’s not likely. Soon, there’s the sound of a woman’s voice singing out a pure high frequency note above other lower voices. By the 50-minute point it could be that organist has had a heart attack, and his fingers remain jammed on the manual, with lots of stops pulled out, and the sound is reverberating around a stone cathedral.

The last keyboards are switched on to complete the pandemonium. There’s a whiff of accordion about the mix now as Asuna begins to remove some of the hundreds of lollypop sticks, one at a time, sometimes pausing to completely switch off an instrument. With a handful gone, the sound has already changed. Walking around the electronic orchestra, suddenly I can detect a real pulsing, with a particular frequency surging twice a second, as regular as clockwork. I adjust my position and it’s gone.

Admittedly my patience wears a bit thin as Asuna dithers over which sticks to remove on which keyboards. But when we’re down to a handful of instruments, there’s a real peace about the performance. It’s no longer a thought experiment to imagine what I’m hearing. It’s a hunt to detect whether this will be the last note. But no. As the conductor releases each instrument, there’s another quieter one remaining behind until the final key is released dead on the 100 minute mark and there is complete silence … and then enthusiastic applause from the audience as Asuna throughs the sticks left in his pocket up in the air in a sudden burst of emotion.

Like nothing else you’ll experience this year at Belfast International Arts Festival. Over an hour devoted to listening, letting your imagination run riot as one chord plays out in a surround sound masterpiece.

100 Keyboards continues in The MAC each evening at 7.45pm until Saturday 19 October.

Check out my preview of other picks from the rich 2019 Belfast International Arts Festival programme which runs until 3 November.