Academic analyses of music aesthetics often privilege the intellectual process of creating symbolic connections over the practical negotiation between performing musicians in a rehearsal setting. In contrast, this article examines the way in which aesthetic elements (styles of improvisation, instrumental riffs, basslines, rhythm grooves, and so on) emerge as a result of power struggles, personal rivalries, and competing stylistic sensibilities. Drawing on my research among ethnic-jazz music groups in Athens, who experimented with cross-overs between funk rhythms, Eastern Mediterranean modal melodies, and jazz harmonization, this article will reveal how musical hybridity can become a contested terrain during rehearsals, creating social dramas of different magnitudes. The first part of the article examines ethnographic vignettes from rehearsals with Athenian musicians, while the second part analyses written testimonies from musicians on their perception of rehearsals and their role in collective music-making.