What is the nature of the musical experience offered by collective free improvisation (CFI)? Many authors, including musicians, have suggested that CFI possesses a deep ethical resonance, both for the listeners and the musicians themselves. This is a feature arguably shared with many musical practices all over the world. However, it is perhaps more explicitly displayed by CFI, which, in the absence of any musical text serving as common ground for the musicians, directly allows and enables the exploration of a large array of interpersonal relations through musical means. In support of this claim, we will present the results of a study conducted with 20 musicians, who recorded 100 improvisations in duo. This study shows that spontaneous dyadic musical interactions can not only mediate, but also directly communicate complex positive and negative social attitudes such as authority, reconciliation, disdain, caring, or disrespect, and that such communication is significantly based on non-prosodic cues linked to temporal and harmonic coordination. These results are of great significance for the aesthetics of music, as they show that musical expressiveness goes well beyond the basic garden-variety emotions (joy, anger, sadness, etc.) most commonly examined in recent literature. Musical sounds in CFI are like a cathartic playground, in that they lead us to experience not only the full spectrum of mundane emotions, but also multiple ways of relating to the other(s) – from alliances to conflicts, from mutual assistance to indifference, from friendship to enmity.