[...] let us give a concrete example of a rule of neutralization. Consider a language which has both long and short vowel at the systematic phonemic level, but in which the feature Long is neutralized before two consonants (regardless of whether the VCC sequence is divided among one, two, or three morphemes), so that only [-Long] vowels appear phonetically in this position. The rule of neutralization which reflects this constraint is (5) V → [-Long]/_CC. Such a rule is a redundancy rule when the VCC sequence is contained within a single morpheme, for in this case the vowel is always in the shortening environment and thus need not be marked for lenght in the dictionary.
- Stanley (2004), Pag. 52