The key number is used in the receiving synthesizer to select which note should be played, and the velocity is normally used to control the amplitude of the note. The Note On status byte is followed by two data bytes, which specify key number (indicating which key was pressed) and velocity (how hard the key was pressed).
The keyboard may be set to transmit on any one of the sixteen logical MIDI channels, and the status byte for the Note On message will indicate the selected Channel number. When a key is pressed on a MIDI keyboard instrument or MIDI keyboard controller, the keyboard sends a Note On message on the MIDI OUT port. In MIDI systems, the activation of a particular note and the release of the same note are considered as two separate events. The messages in this category are the Note On, Note Off, Polyphonic Key Pressure, Channel Pressure, Pitch Bend Change, Program Change, and the Control Change messages. Channel Mode messages affect the way a receiving instrument will respond to the Channel Voice messages.Ĭhannel Voice Messages are used to send musical performance information. Channel Voice Messages carry musical performance data, and these messages comprise most of the traffic in a typical MIDI data stream. System messages are not Channel specific, and no Channel number is indicated in their status bytes.Ĭhannel Messages may be further classified as being either Channel Voice Messages, or Mode Messages. Channel messages are those which apply to a specific Channel, and the Channel number is included in the status byte for these messages. At the highest level, MIDI messages are classified as being either Channel Messages or System Messages. There are a number of different types of MIDI messages. MIDI is also being used for control of devices where standard messages have not been defined by MMA, such as with audio mixing console automation.Ī MIDI message is made up of an eight-bit status byte which is generally followed by one or two data bytes. MIDI Machine Control and MIDI Show Control are interesting extensions because instead of addressing musical instruments they address studio recording equipment (tape decks etc) and theatrical control (lights, smoke machines, etc.). So over the past 20 or more years, companies have enhanced the original MIDI specification by defining additional performance control messages, and creating companion specifications which include: The first specification (1983) did not define every possible "word" that can be spoken in MIDI, nor did it define every musical instruction that might be desired in an electronic performance. Other MIDI messages include selecting which instrument sounds to use, stereo panning, and more. You can also adjust the overall loudness of all the notes with a Channel Volume" message. For example, to sound a note in MIDI you send a "Note On" message, and then assign that note a "velocity", which determines how loud it plays relative to other notes. It was designed for use with keyboard-based musical instruments, so the message structure is oriented to performance events, such as picking a note and then striking it, or setting typical parameters available on electronic keyboards. MIDI is a music description language in digital (binary) form. The MIDI Message specification (or "MIDI Protocol") is probably the most important part of MIDI.