Here we present the theory of computational methods used in this study for modeling the linear optical spectra of molecules in solution, including the nuclear ensemble approach, the Franck-Condon approach, 1-17 and the combined ensemble-Franck-Condon approaches. For simplicity, we only account for two electronic states in spectral calculations: the initial reference electronic state, i, and the final electronic state, f, where the reference state is the ground state for absorption spectra, and the reference state is the excited state for emission spectra. We assume Born-Oppenheimer dynamics for both S 0 and S 1 , and therefore do not consider any contributions from nonadiabatic effects . Note that our ex-pressions for absorption cross-sections are scaled by the frequency ω, and emission cross-sections are scaled by ω 3 , with other references suggesting that the scaling should be ω 4 . In this work, we present a comparison of spectral lineshapes with the transformation from spectral intensity to lineshape intensity given in the computational details.