This chapter discusses the basics of timecode and synchronization. In the days of analog recording, the need for synchronization of audio signals was not obvious, whereas it has always been an issue for video systems. With digital audio and video, the use of signal synchronization is unavoidable. For example, in order to handle multiple streams of either type of signal in a mixer or recording system, it is usually necessary for them to be running at the same speed, having the same sampling frequency, and often with their frames, blocks, or samples aligned in time. The MIDI interface and protocol can carry synchronization data as well as remote control data for musical instruments and other devices. Using timecode, MIDI applications can be run in sync with the replay of an external audio or video machine, in order that the long-term speed relationship between the MIDI replay and the machine remains constant.