Group musical improvisation, as a spontaneous process of collaborative creativity effected through non-verbal social interaction, is a unique psychological phenomenon and universal capacity. Existing studies focus on improvisation among professional jazz musicians, often using qualitative methods. However, improvisation transcends genres and levels of training or experience, and existing qualitative data are rarely analyzed as discourse. We compare findings from studies of jazz musicians' improvising with interview data from free improvisers from varied backgrounds focused on their improvising together (n = 10). The ways jazz musicians construct improvising in talk were distinct from the constructions of this more diverse group, suggesting a specifically professional discourse. By focusing on accounts of deciding whether to play, the ambiguity of musical contributions in the non-verbal context of playing is highlighted. Analysis indicates that musical acts within improvisation are interpreted by the musicians involved in ways that inherently support or resist particular identities. The unique creative, communicative and social process of musical improvising in groups can therefore best be understood when the entirety of improvisational practice and its various contexts are acknowledged. Future research can best recognize the diversity of, and change in, what improvisation can encompass with continued discursive investigation of group improvising.