In 1976 John Goldsmith introduced autosegmental phonology. Phonological phenomena are no longer seen as operating on one linear sequence of segments, called phonemes or feature combinations, but rather as involving some parallel sequences of features which reside on multiple tiers. Autosegmental phonology later evolved into feature geometry, which became the standard theory of representation for theories of the organization of phonology as different as lexical phonology and optimality theory.
What are no longer seen as operating on lexical phonology?