This article describes two hitherto unreported comitative strategies exemplified in Songhay languages of West Africa – external agreement, and bipartite – and demonstrates their wider applicability. The former strategy provides the first clear-cut example of a previously unattested agreement target-controller pair. Based on comparative evidence, this article proposes a scenario for how these could have developed from the typologically unremarkable comitative and coordinative strategies reconstructible for proto-Songhay, in a process facilitated by contact with Berber. The grammaticalisation chain required to explain this has the unexpected effect of reversing a much better-known one previously claimed to be unidirectional, the development COMITATIVE > NP-AND.