The Kelly-Lochbaum transmission-line model of the vocal tract started the discrete-time modeling of speech production. More recently similar techniques have been developed in computer music towards a more generalized methodology. In this paper we will study the application of mixed physical modeling to speech production and speech synthesis. These approaches are Digital Waveguides (DWG), Finite Difference Time-Domain schemes (FDTD), and Wave Digital Filters (WDF). The equivalence and interconnectivity of these schemes is shown and flexible real-time synthesizers for articulatory type of speech production are demonstrated.