We introduce the Triplexer, a novel foot controller that gives the performer 3 degrees of freedom over the control of various effects parameters. With the Triplexer, we aim to expand the performer’s control space by augmenting the capabilities of the common expression pedal that is found in most effects rigs. Using industrial-grade weight-detection sensors and widely-adopted communication protocols, the Triplexer offers a flexible platform that can be integrated into various performance setups and situations. In this paper, we detail the design of the Triplexer by describing its hardware, embedded signal processing, and mapping software implementations. We also offer the results of a user study, which we conducted to evaluate the usability of our controller.