In Korean there exists a tendency for progressive processes to produce less sonorous segments and for regressive processes to create more so- norous segments. Vowel harmony in modern Korean should be regarded as sonority harmony in which the three most sonorous vowels ⁄a, o, ε⁄ do not occur together with lesser sonorous vowels in words of Korean origin. Reciprocal assimilation is explained simply by well-motivated delinking of a Lateral node and nasalization : In other words, it is un-necessary in the description of reciprocal assimilation to introduce a new rule of copying and a Spontaneous Voice node. Vowel deletion should be accounted for by the operations of both fusion and delinking rather than by a simple unconditioned delinking. The coocurrence restriction between coronal segments is caused by the prohibition of spreading which does not apply to all other sequences of a consonant and a glide.
The Linguistic Society of Japan