This invention involves a system of communicating information using audio signals. In one embodiment, the information is encoded in touch tones on the sound track of a television game show. The information relates to the action of the show, and is broadcast in-band with the audio portion of the show. The show, and thus the information encoded in its audio portion, is received by an ordinary home television. A device for playing a game "listens" to the television speaker and decodes the information. The device allows home viewers to play a game based on the action of the show. The touchtones are substantially indiscernible to humans because they are quieter than most of the audio portion of the show, they are very brief, and they are masked by the show's usual sound effects.