Everything about Musical Instrument Digital Interface (MIDI)

What is Musical Instrument Digital Interface (MIDI)?

MIDI (Music Instrument Digital Interface) is a data transfer protocol that allows you to connect various musical equipment. These can be synthesizers, drum machines, samplers, DJ controllers, etc. However, it is important to understand that this protocol does not transfer audio signals between devices. Instead, it transmits digital data – midi messages, which are binary codes (zeros and ones).

MIDI Messages

MIDI messages can be divided into two types, system messages, and channel messages. Most of the time you will be dealing with channel messages. Although, some important functions such as synchronization (Clock) and playback control (stop, start, and continue) are system messages.

Main channel messages

1. Activating and Deactivating Notes (Note On/Off): This contains information about which notes were pressed and released and when including the velocity of the keys.
2. Aftertouch: Additional pressure on a key after it has been pressed. This setting is mainly used for sound modulation.
3. Control Change: Defines a change in the value of a parameter on the device. For example, a knob or fader on a midi controller can be assigned to control the cutoff frequency of a synthesizer filter. For this, the message of the Control Change format will be responsible
4. Program Change: Changes the patch (preset) number on the unit.
5. Channel Pressure: The total pressure value for all keys pressed. Works on a similar principle with aftertouch, only for all keys at once.
6. Pitch Bend: Change the pitch wheel or lever.

System Messages

1. Synchronization (Clock): synchronizes the connected device with the master device in tempo
2. Playback control (Transport): Sends commands to the device to start, stop or continue playback
3. Special system messages (SysEx): Allow hardware manufacturers to create their own types of messages. Some older MIDI devices use SysEx extensively.

Musical Instrument Digital Interface (MIDI) Connectors Types

A midi interface is a device that links various midi-compatible devices together using a standard 5-pin connector. Such devices include various synthesizers or drum machines, as well as computers or even smartphones.

The 5-pin connectors mentioned below come in 3 types: MIDI out, MIDI in, and MIDI thru. It is very important to understand the difference between the two because, if the connection is wrong, the midi connection will not work.

1. MIDI out: This allows you to send data generated within one device. Such as by pressing a key or turning a knob, to other MIDI devices. This jack can only be connected to MIDI in.
2. MIDI in: Receives data from an external source. This jack can be connected to either MIDI out or MIDI thru.
3. MIDI thru: The purpose of this connector is to transmit an exact copy of the data received by the device in the MIDI In. This allows you to combine a large number of devices into a chain controlled by a common source or controller, thus creating a complex setup. This jack can only be connected to MIDI in.