A tension between freedom and constraint is characteristic of improvisation practice and pedagogy, presenting challenges for teachers/workshop leaders. To create musical focus in ensemble improvisation, some sounds are encouraged, whilst others are edited out, ignored or marginalised. This article investigates improvised sounds as central or subaltern, asking how marginal sounds such as musical 'heckles' and off-task sounds can be accepted meaningfully into musical frameworks. I question what can be "learned" from subaltern sounds. How can power structures within the improvisation workshop be subverted by listening to sounds outside teacher-defined frames, and how can listening become inclusive without sessions descending into chaos?