Syllable Contact/Sonority: Vennemann (1988) proposes that metathesis in Sidamo serves to create a better syllable contact, whereby a coda is more sonorous than the following onset. See also Rice (1992) in which sonority is formally represented in terms of geometric tree structure. In Rice's proposed model of feature organization, the structural representation of the more sonorous nasal consonant is more complex than that of the obstruent: the nasal has an SV node linked to the Root node, while an obstruent lacks an SV node. It is proposed that metathesis in Sidamo is motivated by an ill-formed structural relationship between the rhyme and onset consonant: the right-hand segment must not be more sonorous than the preceding consonant. In order to satisfy this requirement, the SV node of the rightmost segment delinks from the Root node and reassociates to the Root node of the preceding segment. Thus, the first segment is realized as nasal and the second as oral; no change in other features is proposed. [Note that a change in manner (e.g. continuancy, stridency) may also be required to yield the correct ouput when the change involved is /sn/ -> [ns]. -- web editor's note.]

Perceptual Optimization: Hume (1998, 2000) argues that metathesis serves to enhance the overall perceptibility of the segments in the sequence and, in turn, strengthen paradigmatic and syntagmatic contrast. By positioning the obstruents, particularly stop consonants, in prevocalic position, the phonetic cues to the consonant's place of articulation are more perceptible. There is no place contrast for the suffixal nasal consonants regardless of whether the nasal occurs in prevocalic or preconsonantal position (place of articulation is systematically neutralized for nasal consonants in preconsonantal position in the language) so no place information is lost by positioning the nasal before the obstruent.