8. The method of claim 7 , wherein each of the HMMs in the first plurality is associated with a respective elemental speech unit, and has one or more states corresponding to one or more temporal phases of the associated, respective elemental speech unit, wherein the multiplicity of states comprises a collection of the one or more states of each of the HMMs in the first plurality, and wherein determining speech content corresponding to the first sequence of temporal frames of the audio input signal comprises determining a probable sequence of elemental speech units based on a most likely sequence of states of the multiplicity.
7. The method of claim 1 , wherein the first plurality of HMMs collectively comprise a multiplicity of states, and wherein determining for each feature vector in the first time sequence a respective set of emission probabilities for the first plurality of HMMs comprises: for each respective feature vector in the first time sequence, determining, at the first time step, for each respective state of the multiplicity of states a respective conditional probability of emitting the respective feature vector given the respective state.