“…In both cases, it would be valuable to connect more closely and in more generality to the large literature on solutions to the wave equation on a rotating black hole background [89,96,97,115]. This could include using higher-spin fields and making contact to the Teukolsky equation [116], as opposed to the scalar wave equations used here, considering other modifications to the wave equations, as for example in modified theories of gravity or black holes [68,[117][118][119][120][121][122][123][124], the introduction of sources [125,126], investigating how to describe caustics as well as the propagator and scattering on the black hole background more generally [127][128][129][130][131].…”