[LAU] interactive performance

Justin Smith noisesmith at gmail.com
Mon Jun 23 17:16:48 EDT 2008

On Mon, Jun 23, 2008 at 8:57 PM, Atte André Jensen
<atte.jensen at gmail.com> wrote:
> Hi
> I just brainstormed with a friend and came up with the idea of
> integrating the audience in my chuck based electronica performance. All
> of the music is parameterized anyways, and since chuck understands OSC,
> I thought this might not be so difficult. I do realize that it's not
> easy though, especially since I have no experience with this.
> So I'm looking for some way to let the audience affect "something" that
> sends data to chuck (preferably by osc). Hopefully something that'll
> allow a crows (at least more than a handful) of people to interact in a
> way that they can actually recognize they're in fact affecting the
> music, although no in a precise, "solo-instrumentalist" kind of way,
> more of a collective gesture.
> I googled a bit, but didn't hit anything useful (maybe because I don't
> know how to ask), so did anyone here try something similar? Any tips,
> hints, software, approaches, not-tos, links, whatever would be highly
> appreciated.
> Anyways a few thoughts:
> 1) Something that reads from an usb-device and sends OSC would (I think)
> be easiest to handle.
> 2) I keep coming back to a web-cam based solution, since it's easy to
> carry and setup + all tweaking is done in software, as opposed to
> building some huge, DIY hardware controller. We already have a VJ, so e
> could project some of the input to provide visual feedback to the audience.
> 3) Another possibility is using some of the other ready-to-use,
> mass-produced (= cheap) controllers readily available, like a dance-mat
> (although that is limiting the amount of people able to interact with
> the system at the same time). Are there any obvious devices I should
> look into?
> --
> peace, love & harmony
> Atte
> http://atte.dk       | http://myspace.com/attejensen
> http://anagrammer.dk | http://modlys.dk
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There is a $1 device called a photoresistor that turns light levels
into varying resistances. Putting it in serial with a low powered (ie
watch) battery would give you an analog signal that varies with light
level. Put lights behind the audience and their movement will change
the light levels detected (most useful with multiple sensors (one
audio channel for each, of course), and perhaps also gels, so they
respond to particular colors of light. If you can destinguish between
signal and ground leads on a cable, this is what the set of
connections should look like:

(you could alligator clip to a cable, or cut a cable where one end was
busted, and solder onto the bare wires, or, of course, solder onto a
regular old jack)

ground --- battery minus
battery plus --- photoresistor --- signal

the housing is left as an exercise

The next step, of course, is writing the software that interprets a
slowly changing signal from an audio channel and influences the music.
Make sure you do not monitor the signal from the photoresitor, the
levels will be funky, and it will be extremely bass (most likely way
below hearing threshold, well into plain old speaker coil frying
territory). You will probably want to lowpass the signal as well, to
get rid of crackle and line noise.

Another idea that works with this is handing out flashlights (if the
flashlights and sensors both have a variety of gel colors, different
audience members have varying levels of influence on different

With pd and gem, it is easy to bind parameters to color/light levels
on particular webcam pixels (in fact I have done this before), but
this will use vastly more cpu, and in the long term actually be more
work than the idea described above (but it is worth considering if you
cannot afford a $3 materials budget, or would have to buy a brand new
soldering iron and solder that you would never use for another
project). In my experience doing the webcam project, I found it most
useful to use it in black and white mode, and have colored rectangles
that can be clicked and dragged as overlays on the webcam display
window, determining which parts of the camera's input control which

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