A recurrent theme in research on socially distributed cognition is to establish the claim that the cognitive phenomenon of transactive memory is grounded in a specific mode of organization: mechanistic compositional organization. My topic is the confluence of transactive remembering or transactive memory systems (TMSs) and mechanistic compositional organization. In relation to this confluence, the paper scrutinizes the claim that the kind of organization grounding TMSs and/or tokens of transactive remembering takes the specific form of mechanistic compositional organization – at least as the latter is usually construed. It is argued (i) that the usual account of mechanistic compositional organization is based on a synchronic composition function, and (ii) that the organization of TMSs and/or transactive remembering is not well understood by way of synchronic composition. The positive account pursued is that TMSs and/or transactive remembering are better understood as grounded in a diachronic composition function.