I've adapted my Variations II installation software for performance by live ensembles. To better fit a performance context, the idea is to determine a multi-section structure in advance, with each section based on a specific number of sketches. Relative to Cage's straight-up Variations II instructions, it's like a sequence of realizations with no pauses in between. Under this approach, while any particular section is being heard, players in the ensemble are creating point/line sketches that will determine music in the section immediately following.
This brings some interesting performance elements into play: players have to develop a sense of the musical consequences associated with their graphical compositions; the ensemble may want to coordinate overall trends in their sketches in order to shape density, pitch range, and dynamics in a more controlled manner; there is a palpable feeling of risk (within the ensemble at least) around the issue of finishing the required number of sketches for the next section by the scheduled deadline.
The software is designed to allow an arbitrary multi-section structure, specified in a simple text file. Any number of players can create point/line sketches via laptops, while a central hub computer buffers the incoming data to generate and play the score and live animation for each section. Its first use was within a concert coordinated by the Music Technology Group at Pompeu Fabra University in Barcelona, Spain. The next performance will be at the 2013 International Computer Music Conference in Perth, Australia.
Check out this [demo video