2. An apparatus according to claim 1 , wherein the speech parameter is a feature vector.
1. An apparatus comprising: a search controller, being a processor operating in dependence upon a program stored in a program memory to control a speech recognition search process; and a plurality of lexical tree processors operating in parallel to perform the speech recognition search process, said lexical tree processors performing tasks initiated at the direction of the search controller; wherein the search controller is configured to direct one or more of the lexical tree processors to perform initial estimates of scores for a speech parameter evaluated against a first set of lexical trees; wherein the search controller is further configured to perform a pruning operation using the initial estimates of scores and to direct one or more of the lexical tree processors to perform a complete evaluation of scores evaluated against a second set of lexical trees; wherein the first set of lexical trees is substantially broader than the second set of lexical trees; and wherein the initial estimates of scores is performed substantially faster than the complete evaluation of scores.