A human interface device may include at least one analog control pressure surface that may operate in conjunction with at least one optical tube assembly (OTA) to allow precision human control of signal modulation, such as an audio signal being generated by a musical instrument. Each OTA may be incorporated within a body and may include a tube and an emitter-sensor pair wherein when pressure is applied to at least one of the pressure surfaces, the amount of light transferred within a sensor-emitter pair of an OTA is altered to selectively effect the signal modulation. Any type of control range may be expressed that depends on dynamic range and “touch” control. Accordingly, the human interface device may allow more “feeling” or expressiveness through application of pressure rather than positioning.