Once a vibrational spectrum is fit, the central frequencies of each vibrational band give information as to the frequencies that are enriched in the vibrational density of states, which then lead to conclusions about the local environments of the vibrational modes of interest. However, recent computational modeling of heterodyne phase-resolved chiral SFG spectra has produced predictions that do not seem to fit the assumptions of this workflow. In particular, our group demonstrated that the isolated O-H stretch response of the first hydration shell around the b-sheet protein LK7b produces a characteristic "up-down" line shape (Figure ), in contrast to the single peak of the infrared (IR) spectrum of the same ensemble of water (Figure ). It appears that the phase-resolved chiral SFG spectrum is not reporting directly the typical vibrational frequencies in the system. Thus, fitting the chiral SFG response of water with individual Lorentzian curves, as has been done so far, may not allow the estimation of the underlying vibrational frequency distribution reliably and therefore may fall short in revealing structures and dynamics of water in the protein hydration shell. Hence, our computational results call into question whether the application of the standard assumptions in analyzing chiral SFG signals from water in hydration shells of biomolecules is valid. ) IR response of the same water molecules, using the time-averaging approximation for a realistic peak width. The spectrum in part a) was originally published in ref 2.