A conceptually new method to combine pure compound equations of state (EOSs) for the calculation of mixture properties is proposed. As for the case of EOSs using the one-fluid approach, the new method accounts for the effect of density on the excess properties. On the other hand, as for activity coefficient models, the new technique gives the ideal solution behavior in the absence of adjustable parameters. The new approach is consistent with several accepted thermodynamic limits. The simplest variant of the new model has a quantitative performance which depends on the complexity of the system under study.