It has proven practical over a long history of research on language sound systems to rationalize phonological units and processes in terms of speech articulation. The Sanskrit grammarians, for example, focused on vocal anatomy and articulatory processes to the exclusion of descriptions of acoustic or auditory impressions produced by speech sounds (Allen, 1953). Similarly, the 19th century linguists Bell (1867), Sweet (1877), Sievers (1881), Passy (1890), and Rousselot (1897-1901) all focused primarily on speech articulation to explain sound change, describe similarities and differences across languages and in language teaching. For example, the Sweet/Bell system of vowel classification (which is still widely used in phonological description) and their iconic phonetic alphabets were based on speech articulation. This tradition of articulatory