The concepts and ideas of coherent, nonlinear and quantum optics have been extended to photon energies in the range of 10-100 kilo-electronvolts, corresponding to soft gamma-ray radiation (the term used when the radiation is produced in nuclear transitions) or, equivalently, hard X-ray radiation (the term used when the radiation is produced by electron motion). The recent experimental achievements in this energy range include the demonstration of parametric down-conversion in the Langevin regime(1), electromagnetically induced transparency in a cavity(2), the collective Lamb shift(3), vacuum-assisted generation of atomic coherences(4) and single-photon revival in nuclear absorbing multilayer structures(5). Also, realization of single-photon coherent storage(6) and stimulated Raman adiabatic passage(7) were recently proposed in this regime. More related work is discussed in a recent review(8). However, the number of tools for the coherent manipulation of interactions between gamma-ray photons and nuclear ensembles remains limited. Here we suggest and implement an efficient method to control the waveforms of gamma-ray photons coherently. In particular, we demonstrate the conversion of individual recoilless gamma-ray photons into a coherent, ultrashort pulse train and into a double pulse. Our method is based on the resonant interaction of gamma-ray photons with an ensemble of nuclei with a resonant transition frequency that is periodically modulated in time. The frequency modulation, which is achieved by a uniform vibration of the resonant absorber, owing to the Doppler effect, renders resonant absorption and dispersion both time dependent, allowing us to shape the waveforms of the incident gamma-ray photons. We expect that this technique will lead to advances in the emerging fields of coherent and quantum gamma-ray photon optics, providing a basis for the realization of gamma-ray-photon/nuclear-ensemble interfaces and quantum interference effects at nuclear gamma-ray transitions.