1. A method for generating a speech signal comprising the steps of: receiving super-class information; receiving fundamental frequency information; applying each tuple of super-class information and fundamental frequency information to a module that correlates fundamental frequencies with LSF vectors for different super-classes, to obtain a desired LSF vector associated with each of said tuples; and generating a speech spectrum, in association with each tuple, that is characterized by an LSF vector that is, or approximates, said desired LSF vector associated with each of said tuples.