Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for obtaining audio data corresponding to an utterance; transmitting the audio data corresponding to the utterance; receiving an indication that that utterance likely includes a communication-related voice command; in response to receiving the indication that the utterance likely includes the communication-related voice command, applying at least a language model to a representation of the audio data corresponding to the utterance, to identify data referencing a contact; and transmitting the data referencing the contact.