GAB is an electronic system that allows the reinterpretation of musical material in real time. It is designed to be used by a pianist during the performance of musical improvisations. The system consists of a computer program written in Java that performs all the mathematical calculations required to produce the reinterpreted material and a small controller enabling the pianist to modify the variables of the system. GAB is the first result of a personal search that attempts to combine the design and use of musical instruments with improvisation as a creative means of expression. The project was part of my undergraduate thesis.