Calle O'Reilly

Five percussionists, a bass player and two vocalists will perform the Afro-Cuban song “Compa Galletano” over a Guaguancó rumba rhythm. Two digital media artists and one programmer will use electronic sensors and motion-tracking techniques to drive a live video performance which will take the audience on a unique journey to the roots of Afro-Cuban music.

The performance will be the opening event of the Project Brand New 3-Day celebration of new and innovative work in the performing arts. It will take place at 8.00pm on Thursday 29 April.

The percussion driven video performance was a considerably complex and ambitious concept and required a significant amount of research. The concept was to use the reverberation from the drum beat to illuminate an infrared LED (invisible to the human eye) which could then—via a web camera—be used to locate the source of the beat, on the stage. This would allow me to project visuals with explosive and sublime accuracy.

I started down the path of using microphones as the sensor for reading percussive input but following some sound advice from my old electronics tutor, Nicky Ward—to who I am most grateful for his guidance—I decided to go with Piezoelectric sensors instead. He sent me some very useful links including this tutorial on how to build a drumlight trigger, which was exactly what I was looking for. 

It was from here that I downloaded this circuit diagram for the drum-light trigger, which I believe must be credited to John F from It's a very effective little circuit and has great reactivity and adjustability (whereby I can lenghten the time the LED flashes simply by adjusting the variable resistor).

Needless to say I am eternally grateful to the author of this website for sharing his knowledge with the world and I.

This is what my prototype breadboard circuit looked like in the end.

Piezo Pulse Stretcher Breadboard Prototype

After that it was simple case of replacing the standard LED with an infrared LED. This killed two birds with one stone:

  1. It visualised the drum rhythm.
  2. It allowed me to locate the source of the drum beat.

I used custom software—built using the Openframeworks library—for the computer vision part of the project. The graphics themselves were designed using Processing. Neither the graphics nor the motion tracking would have worked so flawlessly if it wasn't for the invaluable contribution to the project by my friend and collegue Colin O'Sullivan.


The projections were most successful on the conga drummers. Here's a short video of them in action, at the Project Arts Centre. If you'd like to watch the full performance you can follow the "video" link above.

Congas with reactive graphics from Neill O'Dwyer on Vimeo.

The reaction time was really quite fast and accurate, so all in all we were really quite pleased with the outcome. Especially since it was a forum for experimental work. We got some very useful feedback from the audience. One of the comments which I'm inclined to aggree with was that the audience shoudl be able to see the performers' faces. The graphics were quite dark, so we'll definitely bear this in mind when developing the show.