This paper describes the conceptualization and development of an open source tool for controlling the sound of a saxophone via the gestures of its performer. The motivation behind this work is the need for easy access tools to explore, compose and perform electroacoustic music in Colombian music schools and conservatories. This work led to the adaptation of common hardware to be used as a sensor attached to an acoustic instrument and the development of software applications to record, visualize and map performers gesture data into signal processing parameters. The scope of this work suggested that focus was to be made on a specific instrument so the saxophone was chosen. Gestures were selected in an iterative process with the performer, although a more ambitious strategy to figure out main gestures of an instruments performance was first defined. Detailed gesture-to-sound processing mappings are exposed in the text. An electroacoustic musical piece was successfully rehearsed and recorded using the Gest-O system.