We analysed how expressive intentions are communicated and perceived in a special context of musical production: improvisation on a single piano note. Two experiments were designed in order to find relations between performer's expressive intentions, four acoustical parameters (pitch, intensity, articulation and rhythmic density), and listener's perception of expressive content. Differences between musicians and non-musicians were analysed as well. In the first experiment, 6 performers (3 musicians and 3 non-musicians) improvised on a digital piano according to 8 expressive intentions. The experiment was planned in 4 phases, progressively limiting the musical means available to the performer. In all phases, improvisations were limited to only one piano note. In the second experiment, listeners described performer's improvisations by means of adjective ratings. Results support the position that few low level parameters, mainly intensity and rhythmic density, are important factors in the communication of expressive content from the performer to the listener and that listeners recognize most expressive intentions even when very few acoustical parameters are used.