Voice has been an almost obsessive topic of discussion in Austronesian linguistics. Voice alternations change the identity of the grammatical subject, without changing the argument structure (semantic roles) of the clause. This is typically accomplished by demoting the subject of a basic transitive clause to non-core argument status. However, a substantial number of Western Austronesian languages have been argued to exhibit SYMMETRICAL (i.e., non-demoting) voice alternations, and the correct analysis of these systems has been a topic of long-standing controversy. This chapter describes a representative sample of Western and Central Malayo-Polynesian voice systems, and summarizes some of the analyses that have been proposed. Two empirical questions are of central importance for this study: (i) What is the grammatical subject for a particular clause type? and (ii) How do we distinguish core arguments from obliques? In addition to the typologically unusual nature of some of these systems, Austronesian is remarkable for the broad range of variation attested in its voice systems. Within the Western Malayo-Polynesian area it is common to distinguish voice systems of the Philippine-type (in the north) vs. those of the Indonesian-type (in the south and west). But even within the so-called Indonesian-type a considerable degree of variation is found. Our survey shows a general trend of simplification, with voice morphology and voice distinctions becoming more sparse, as one moves across Indonesia from west to east.