A MIDI event that carries the MIDI song request message (also known as a "song select message") tells a MIDI device to select a sequence for playback.
This message belongs to the category of MIDI system common messages.
This message consists of two bytes of data. The first byte is the status byte and has a hexadecimal value of 0xF3 signifying that this is a song request message. The second and last byte of data is a number between 0x00 and 0x7F (0 and 127) and represents the number of the song to be chosen. When the sequence is selected the device should also cue to the beginning of the sequence at MIDI beat zero.
The following is an example of a song request message.
The first byte is 0xF3 signifying that this is a song request message. The second byte is 0x01 which means that the device is to select song 1 for playback.
Musical Instrument Digital Interface (MIDI)