  Waveforms are classical observables associated with any radiative physical
process. Using scattering amplitudes, these are usually computed in a
weak-field regime to some finite order in the post-Newtonian or
post-Minkowskian approximation. Here, we use strong field amplitudes to compute
the waveform produced in scattering of massive particles on gravitational plane
waves, treated as exact nonlinear solutions of the vacuum Einstein equations.
Notably, the waveform contains an infinite number of post-Minkowskian
contributions, as well as tail effects. We also provide, and contrast with,
analogous results in electromagnetism.
