A recognition system based on a reference library of synthetic phoneme prototypes is described. The phoneme templates are specified in terms of formant synthesis parameters. The vocabulary and grammar is described in a finite-state network of phonemes. Each phoneme is divided into a number of new states representing transitions and steady-state regions. The parameters of the transition states are interpolated from the steady-state parameters. At each state, a 16-channel filter bank section is computed from the synthesis parameters. Dynamic adaptation to each speaker's individual voice source spectrum is performed during recognition. Without adaptation, the average recognition for ten male speakers was 88% on an isolated-word task using a 26-word vocabulary. Adding voice source adaptation raised the performance to 96%. On a vocabulary of 3 connected digits, the adaptation technique improved the recognition rate for six male speakers from 87.7% to 92.8%. The improvement was largest for subjects with low initial recognition rate, indicating the usefulness of the voice source adaptation technique for certain voices.