A theoretical model is elaborated which allows methods used in gas phase to be applied to calculate the vibrational energies and transition moments for low-lying levels of O-3 trapped in rare gas matrices. The model used in a previous work allowed only one mode to be handled at a time. With the new approach, an overall treatment of low-lying levels is achieved. The trapping site, a single or double substitutional one is distorted to minimize the free energy of the molecule-matrix system. The molecule is considered to be submitted to the net electric field present in the site as the result of the distortion and polarization of the matrix atoms. New harmonic and anharmonic constants that lead to matrix dependent calculated energy levels and transition moments can then be determined. Besides confirmation of two trapping sites, a single (S1) and a double (S2) substitutional site in a distorted face-centered-cubic (fcc) lattice structure, two other S1 sites in argon and krypton in a distorted hexagonal-closed-packed (hcp) lattice structure are shown to be possible. A fit within experimental uncertainty is reached between observed and calculated frequencies for fundamental bands v(1), v(2), and v(3).