  We take the opportunity offered by Schirmacher, Bryk, Ruocco et al. to
explain more in depth the details of our theoretical model (Phys. Rev. Lett.
112, 145501 (2019)) and its improved and extended version (Phys. Rev. Research
2, 013267, (2020)). We unequivocally show the presence of a boson peak (BP)
anomaly in solids due to anharmonic diffusive damping (of the Akhiezer type)
and anharmonic corrections to the low-energy plane wave $\omega=v\,k$
dispersion relation. Finally, we emphasize the need of going beyond the
old-fashion "harmonic disorder" BP picture which is clearly unable to explain
the recent experimental observations of BP in perfectly ordered crystals. For
the sake of openness and transparency, we provide a Mathematica file
downloadable by all interested readers who wish to check our calculations.
