A nonadiabatic model is presented to simulate the methyl regions of the overtone spectra of 2-, 3-, and 4-methylpyridine. The model incorporates harmonically coupled anharmonic oscillator local modes for CH stretching and rigid rotors for methyl internal rotation. Parameters for the model come from a series of ab initio calculations. The methyl regions of the overtone spectra are complex because of coupling between CH stretching and methyl torsion. Moreover there are differences between the similar spectra of 3- and 4-methylpyridine on one hand and the spectrum of 2-methylpyridine on the other. The simulation is successful in reproducing the methyl band profiles and in accounting for the spectral differences. Differences in the methyl band profiles are ascribed to differences in symmetry and magnitude of the frequency, anharmonicity, and torsional barrier and to differences in their dependence on the torsional angle. The success of the model and its ability to accommodate arbitrary functional forms of the frequency, anharmonicity, torsional barrier, and dipole moment function suggests its general applicability for the analysis of overtone spectra in a wide variety of molecules.