Category: System Common
Purpose
Some master device that controls sequence playback sends this message to force a slave device to cue the playback to a certain point in the song/sequence. In other words, this message sets the device's "Song Position". This message doesn't actually start the playback. It just sets up the device to be "ready to play" at a particular point in the song.
Status
0xF2
Data
Two data bytes follow the status. Just like with the Pitch Wheel, these two bytes are combined into a 14-bit value. (See Pitch Wheel). This 14-bit value is the MIDI Beat upon which to start the song. Songs are always assumed to start on a MIDI Beat of 0. Each MIDI Beat spans 6 MIDI Clocks. In other words, each MIDI Beat is a 16th note (since there are 24 MIDI Clocks in a quarter note).
Errata
Example: If a Song Position value of 8 is received, then a sequencer (or drum box) should cue playback to the third quarter note of the song. (8 MIDI beats * 6 MIDI clocks per MIDI beat = 48 MIDI Clocks. Since there are 24 MIDI Clocks in a quarter note, the first quarter occurs on a time of 0 MIDI Clocks, the second quarter note occurs upon the 24th MIDI Clock, and the third quarter note occurs on the 48th MIDI Clock).
Often, the slave device has its playback tempo synced to the master via MIDI Clock. See Syncing Sequence Playback.