1. A speech recognition system comprising: means for receiving an acoustic description of a portion of speech to be recognized; means for storing an acoustic description of each word in a system vocabulary; recognition means for making a determination of which one or more words of a recognition vocabulary, comprised of one or more words from said system vocabulary, most probably correspond to said portion of speech, said recognition means including comparing means for determining how closely the acoustic description of said portion of speech compares to the acoustic descriptions of words from said recognition vocabulary; and first-pass means for causing said recognition means to start to perform a first recognition of said portion of speech using a first such recognition vocabulary; control-input means for enabling an operator to input a string of one or more selected characters if he or she so desires; and re-recognition means responsive to the input of a string of characters through said control-input means for causing said recognition means to start to perform a second recognition of said portion of speech using a second such recognition vocabulary, said re-recognition means including alphabetic filtering means for selecting a sub-vocabulary from said system vocabulary to be used as said second recognition vocabulary, said filtering means including means, responsive to said control-input means, for causing said sub-vocabulary to include an increased percent of vocabulary words specified as a function of said string of one or more characters input through said control-input means.