1. Pattern recognition apparatus for classifying an arbitrary input signal into one of N known classes, comprising: an analyzer for processing the arbitrary input signal to generate a set of features corresponding to the input signal; a plurality of category-specific feature recognizers coupled to the analyzer that identify predetermined features in the results of analysis corresponding to a respective category; a plurality of likelihood processors that respectively process outputs of the plurality of feature recognizers to produce likelihood values that are indicative of the class membership of the input signal; and a combination rule processor for processing outputs of the plurality of likelihood processors to make a final decision regarding the class of the input signal.