While many previous studies have explored indeterminacy as a compositional technique, in this article we explore the concept of indeterminacy, not only from the perspective of the composer, but also from the perspectives of performer and archival researcher, drawing upon our experiences of researching and performing several live electronic music compositions by British experimental musician Hugh Davies (1943–2005). Our core argument is that beneath the surface level of composed indeterminacy—that is, beyond the notations and instructions that a composer employs to prescribe indeterminate musical results—there exist further ‘nested’ planes of indeterminacy that reveal themselves through the acts of archival research, rehearsal and performance. ‘Instrumental’ indeterminacy has to do with the instruments that are used to perform the music, and specifically to situations where the boundaries of the instruments are experienced (by performers or audience members) as ambiguous, fluid, reconfigurable, or undefinable, or where the behaviour of the instrument(s) is unpredictable or uncontrollable in the moment of performance. ‘Hermeneutic’ indeterminacy concerns the composer’s intentions and the ways in which these are revealed, through the processes of archival and performance research, to be incompletely, ambiguously, contradictorily, and/or diffusely represented in documents (including but not limited to scores) and material configurations (including the instruments and apparatus used to perform the music). ‘Ontological’ indeterminacy is signalled by uncertainty (on the part of the researchers) about the ontological status of the piece to be performed. By sharing these perspectives, we aim to contribute to scholarly understandings of the ‘afterlives’ of indeterminacy, beyond the circumscriptions of a composer.