For pyridine in methanol, the frequencies are largely unaffected in the high-frequency part of the spectrum and with minor errors in the low-frequency part. The maximum error is around 3 cm -1 . The impact on IR and Raman intensities, on the other hand, is substantial. In particular, the IR intensities of normal modes 13, 14, 24, and 25 and the Raman intensity of normal mode 24 have considerable relative and absolute errors. These four normal modes represent in-plane bending motions of the pyridine molecule, which couple to the C-O stretching mode of methanol in the case of modes 13 and 14 and to the torsion mode of methanol in the case of modes 24 and 25. These modes have environmental contributions that are removed through the PHVA approximation, which explains the resulting frequency errors and, to some degree, the intensity errors. Similar to the normal modes with high errors, mixing between solute and solvent vibrations is also observed in other modes, yet the associated frequencies and intensities have low errors. For example, in normal mode 9, a mixing between an in-plane bending mode in pyridine and the O-H rocking mode in methanol can be observed. However, since normal mode 9 has a low intensity in both the partial and full treatment, the absolute error introduced to the IR intensities is also low.