1. A method comprising: periodically receiving, by a first playback device over a local network, a message transmitted from a second playback device, wherein the message comprises clock information of the second playback device; computing, by the first playback device based on the message, a time differential between a clock of the first playback device and a clock of the second playback device; receiving, by the first playback device over the local network, a command from the second playback device to cease playback of a first song, wherein the first song is (i) received from the second playback device and (ii) played in synchrony by the first and second playback devices, wherein the command to cease playback includes a time indicating when the second playback device is to cease playback of the first song; and in response to the command, (i) computing, by the first playback device, a specified time to cease playback of the first song, wherein the specified time is based on the time differential and the time indicating when to cease playback of the first song; and (ii) ceasing, by the first playback device, playback of the first song at the specified time, wherein the specified time is concurrent with a ceasing of the playback of the first song by the second playback device.