Quadraphonic performance and composition should be more prevalent, more popular. Now that the costs associated with setting up a quad system have dropped dramatically, there’s little reason why it shouldn’t be.
You can cheaply rent four self-powered speakers just about anywhere. You could even use instrument amplifiers, or any other similar things you have available. That’s the first part of the solution.
The next part is a way to mix a set of signals into the quad space. Unfortunately, finding equipment to do this mixing is not as easy. I encountered this problem while curating the Immersion events in Austin; to solve it I built a simple software based quad mixer. This mixer evolved over time into The QuadTool.
The QuadTool is a portable and practical quadraphonic sound projection and synthesis system, designed for projecting listening objects at venues and events where a large multi-channel speaker configuration is not practical or possible.
More about The QuadTool can be found here.