19. A speech recognition method comprising: using a first method to calculate a first score for each of a plurality of vocabulary words based at least in part on descriptions of successive sounds from an utterance to be recognized, said scores indicating the probability that each vocabulary word corresponds to said utterance; using a second method to calculate a second score for each of said vocabulary words based at least in part on descriptions of the same successive sounds from said utterance; said second scores also indicating the probability that each vocabulary word corresponds to the utterance to be recognized; combining said first and second scores for each of said vocabulary words to produce a combined score for that word; using the combined score produced for each vocabulary word to determine which of said vocabulary words most probably corresponds to the utterance to be recognized; wherein: the method starts with an initial currently active vocabulary comprising a plurality of vocabulary words; the method comprises a succession of word-selecting phaes, each of which selects a sub-set of words from the currently active vocabulary, and makes that sub-set into the new currently active vocabulary; one of said word-selecting phases comprises the using of said first and second methods to calculate first and second scores for each vocabulary word in the currently active vocabulary and then using the combined scores produced for each currently active vocabulary word to select said sub-set of that currently active vocabulary as the new currently active vocabulary.
19. A speech recognition method comprising: using a first method to calculate a first score for each of a plurality of vocabulary words based at least in part on descriptions of successive sounds from an utterance to be recognized, said scores indicating the probability that each vocabulary word corresponds to said utterance; using a second method to calculate a second score for each of said vocabulary words based at least in part on descriptions of the same successive sounds from said utterance; said second scores also indicating the probability that each vocabulary word corresponds to the utterance to be recognized; combining said first and second scores for each of said vocabulary words to produce a combined score for that word; using the combined score produced for each vocabulary word to determine which of said vocabulary words most probably corresponds to the utterance to be recognized; wherein: the method starts with an initial currently active vocabulary comprising a plurality of vocabulary words; the method comprises a succession of word-selecting phaes, each of which selects a sub-set of words from the currently active vocabulary, and makes that sub-set into the new currently active vocabulary; one of said word-selecting phases comprises the using of said first and second methods to calculate first and second scores for each vocabulary word in the currently active vocabulary and then using the combined scores produced for each currently active vocabulary word to select said sub-set of that currently active vocabulary as the new currently active vocabulary. 20. A speech recognition method as described in claim 19 wherein said word-selecting phase which uses said first and second method comprises less than half of the computation required by all word-selecting phases to recognize a given utterance.