1. A method comprising: receiving, by a training system, a set of development sentences W; receiving a set of two or more language models G M , each language model in the set of two or more language models G M for use by an automatic speech recognition system when generating text from speech; determining a set of n-gram language model weights λ M using the development sentences W and the set of two or more language models G M ; determining a set of sentence cluster weights γ C , each of the sentence cluster weights corresponding to a cluster in a set of sentence clusters, each cluster in the set of sentence clusters associated with at least one sentence from the set of development sentences W; generating a language model from the set of two or more language models G M , the set of n-gram language model weights λ M , the set of sentence clusters, and the set of sentence cluster weights γ C ; and providing, by the training system, the language model for use by a particular automatic speech recognition system to determine n-grams included in an utterance encoded in an audio signal.