1. A method of decoding a speech signal by generating a score for a current state in a finite state system, the method comprising: determining a production-related value for the current state based on an optimal production-related value at the end of a preceding state, the optimal production-related value being selected from a set of continuous values, using the production-related value to determine a likelihood of a phone being represented by a set of observation vectors that are aligned with a path between the preceding state and the current state; and combining the likelihood of the phone with a score from the preceding state to determine the score for the current state, the score from the preceding state being associated with a discrete class of production-related values wherein the class matches the class of the optimal production-related value.