Different nuclear motions play different roles in shaping the absorption spectrum: the high-frequency modes of the spectral density, often involving the intramolecular vibrations of the chromophore, can produce a vibronic Franck-Condon progression and vibrational coherences, whereas the low-frequency modes due to the collective motions of the chromophore and its local environment (e.g. solvent molecules) inhomogeneously broaden the spectrum. Separation of the high-and low-frequency contributions to the absorption spectrum enable the separate analysis of the inhomogeneous broadening and vibronic contributions to spectral lineshapes.