Vx is an interactive sound art work composed in 2013, and part of a trilogy that explores the relationships between sight and sound transformations. The name comes from a commonly used aviation abbreviation that references the “velocity for best climb angle;” the airspeed at which an airfoil will gain maximal altitude over the shortest amount of distance. Vx explores the transformation of visual information into sound, whereas another piece within the trilogy (Vy), explores the opposite relationship. Vx is performed entirely by audience members using simple (and cheap) laser pointers to activate pixels within a 10 by 10 web-camera grid. Each of the squares within the grid is programmed to activate and control different aspects of the underlying sound. A screen shot of the grid can be seen in the picture below.
The programming behind Vx is simple. The entire grid was partitioned into smaller areas for each instrument sound type (pads, leads, loops, effects, etc.), as indicated by the colors in the picture above. Within each square, a trigger is activated when the average brightness of all pixels in the square exceeds some specific value. The trigger threshold value can be set for the specific performance environment; dark spaces work best. Further, due to the way in which lasers are detected by the camera, it is helpful to perform the piece against a plain white surface such as a wall or a projector screen. Vx can be performed by any number of lasers, but a given grid square is activated by a single point, multiple lasers within a given square have no further effect.
Within the patch, there are two types of triggers: flip-flops and presence detectors. The flip-flop trigger is activated when a laser enters an empty square, and it is deactivated the next time that a laser enters the same empty square. This particular type of trigger is useful for activating various loops (drum beats, short sound effect clips, organ drones, etc.). The presence detectors are activated whenever a laser enters an empty square, and deactivated as the laser leaves the square. These triggers are useful for controlling individual notes.
One aspect of Vx that always surprises me is the spontaneous emergence of social dynamics. After a few minutes, audience members begin to interact with other laser points. For example, laser points may chase one another or band together as they explore the visual/sonic space. One performance in particular used multiple color lasers, and the interaction between green and red points was truly fascinating.
The MAX/MSP files for Vx can be freely obtained for performances by request (as well as the files for “Vy” and “Best Glide”). If you are interested in using the interface/triggers, the template files are available under a creative commons attribution 3.0 license (link below).