The most common approach to compute vibrational spectra is normal mode analysis, typically within the Born-Oppenheimer approximation. While this approach is computationally efficient, it has several limitations: It only allows the calculation of the fundamental transitions, which excludes a series of phenomena, such as overtones, combination and hot bands, Fermi resonances and bond breaking. Anharmonic effects are not captured and explicit solvent effects cannot be included because the structure must be in a local minimum and configurational sampling is thus not accounted for.