Densities and speeds of sound of ternary o-chlorotoluene (1) + tetrahydropyran (2) + benzene or toluene or o-xylene (3) mixtures and their sub-binaries o-chlorotoluene (1) + toluene or o-xylene (2) at (298.15, 303.15, and 308.15) K have been measured, and of tetrahydropyran (1) + benzene or toluene or o-xylene (2) mixtures at (298.15 and 303.15) K and 0.1 MPa. Excess molar volumes, V-E(123) and V-E, and excess isentropic compressibilities, (kappa(E)(S))(123) and kappa(E)(S), have been computed from experimental data. The V-E(123) for o-chlorotoluene (1) + tetrahydropyran (2) + o-xylene (3) and (K-S(E))123 for o-chlorotoluene (1) + tetrahydropyran (2) + benzene or toluene or o-xylene (3) are negative over the entire mole fraction of 1 and 2. However, the sign and magnitude of V-E(123) for o-chlorotoluene (1) + tetrahydropyran (2) + benzene or toluene (3) mixtures are dictated by the relative proportion of the constituents. The excess functions have been analyzed in terms of Graph theory, PrigogineFloryPatterson theory, and Sanchez and Lacombes theories.