In this paper, we present an innovative Neural Network system interface that allows an electronic music composer to plan and conduct the musical expressivity of a performer. For musical expressivity we mean all those execution techniques and modalities that a performer has to follow in order to satisfy common musical aesthetics, as well as the desiderata of the composer. The proposed interface or virtual musical instrument is able to transform two input parameters in many sound synthesis parameters. Especially, we focus our attention on mapping strategies based on Neural Network to solve the problem of electronic music expressivity.