What is MIDI function?

MIDI stands for Musical Instrument Digital Interface. It is a technical standard that describes a protocol, digital interface, and connectors that allows a wide variety of electronic musical instruments, computers, and other equipment to connect and communicate with each other.

MIDI enables various musical instruments like keyboard synthesizers, computers, and other devices to control one another and exchange system data. This allows them to effectively communicate and synchronize with each other. MIDI allows for commands that can be sent digitally over cables to operate musical instruments remotely.

The development of MIDI began in the early 1980s by Sequential Circuits employee Dave Smith. At the time, Smith realized the need for compatibility between electronic instruments from different manufacturers. He proposed the idea of a digital “Universal Synthesizer Interface” to the Audio Engineering Society in 1981. This laid the foundation for the MIDI standard (“The History Of MIDI -,” n.d.).

The official MIDI specification was published in August 1983. MIDI version 1.0 was ratified in January 1984 after work by Dave Smith and Ikutaro Kakehashi, who later founded the MIDI Manufacturers Association. MIDI was quickly adopted widely by instrument and equipment manufacturers in the 1980s and became an industry standard.

How MIDI Works

MIDI messages communicate musical performance data between devices. These messages contain information about what notes are played, the velocity or intensity of the notes, control changes, and more. This allows electronic musical instruments like synthesizers, keyboards, and drum machines to be connected together to create and playback complex arrangements.

The core MIDI messages that communicate note data are Note On and Note Off messages. When a note is played on a MIDI controller like a keyboard, it sends a Note On message with a note number and velocity value. When the note is released, a corresponding Note Off message is sent. This allows the connected MIDI device, like a synthesizer, to play the correct pitch and dynamics.

Control Change messages allow adjustment of device parameters like volume, panning, effects levels and more to shape the sound. These messages allow real-time tweaking as a performance plays back.

Devices with MIDI inputs and outputs can connect together via 5-pin DIN cables. This allows the musical data to be transmitted between instruments and devices. Up to 16 channels of MIDI data can be sent through one cable, allowing for complex arrangements.

By encoding musical performance data into a standard digital format, MIDI revolutionized electronic music production. It enabled interconnection between devices from different manufacturers for the first time (Source).

MIDI Devices

MIDI devices include a wide range of musical instruments and hardware that can send and receive MIDI messages. Some of the most common MIDI instruments are:

Keyboard synthesizers and controllers: Keyboards were some of the first instruments to support MIDI. Synthesizers like the Yamaha DX7 and Sequential Prophet allowed musicians to control sounds and parameters through MIDI.
Drum machines: Early drum machines like the famous Roland TR-808 used MIDI to synchronize rhythm patterns with other devices. Modern drum machines continue to utilize MIDI for sequencing drums.

Samplers: Samplers, like the classic Akai MPC, allow musicians to load and manipulate audio samples using MIDI.
Sequencers: Digital audio workstations and MIDI sequencers use MIDI data to record, edit, and play back MIDI information on instruments and devices.

In addition to dedicated MIDI instruments, even standard computer soundcards and interfaces allow you to connect MIDI devices to a computer system. This allows you to record, process, and sequence MIDI using music software and plugins.

MIDI Messages

MIDI messages allow various MIDI devices to communicate with each other. There are two main types of MIDI messages:

Channel Messages

Channel messages are sent on one of 16 MIDI channels and generally deal with performance data. Examples include:

Note on/off – Turn notes on and off.

Program change – Change instrument or patch.
Control change – Adjust controller parameters like volume, pan, etc.
Pitch bend – Bend note pitch up or down.

System Messages

System messages are sent on a system channel and deal with overall MIDI system functions. Examples include:

Timing and synchronization messages to keep devices in sync.
Transport control messages like start, stop, continue.

For more details on MIDI message types supported on iOS, see the MIDI Messages documentation from Apple.

MIDI Channels

MIDI utilizes 16 channels for sending MIDI messages to different instruments and devices. This allows each MIDI channel to be assigned to a separate instrument or sound module, enabling layering of parts and separation of different instruments within a MIDI setup.

By default, MIDI channels operate in Omni mode, meaning the messages sent on a channel are received by all devices connected to the system. However, MIDI instruments and sound modules can be set to respond only to messages sent on specific channels, allowing more control over the destination of the MIDI data.

The 16 channel separation provided by MIDI is what enables the creation of layered and complex musical arrangements using multiple synthesizers, drum machines, and other gear. Without the channel system, it would be impossible to have different instruments playing independently in a MIDI sequence.[https://bluebuzzmusic.com/midi-technology/]

MIDI Cables and Connectors

MIDI devices are connected using 5-pin DIN cables and connectors. The 5-pin DIN connector has been standard for MIDI since its introduction in the 1980s.

The MIDI cable pinout is as follows:

Pin 1: Not used
Pin 2: Not used
Pin 3: Not used

Pin 4: Carries +5V DC from MIDI out device to MIDI in device
Pin 5: Serial data

For more details on MIDI cabling, refer to MIDI Cable Pinout.

Standard MIDI cables are limited to 15-20 meters in length. Longer distances can cause interference and data loss. Using MIDI interfaces, mergers and thru boxes can extend the cable length by acting as signal repeaters.

MIDI Software

A wide variety of software utilizes MIDI data for music production, including sequencers, notation programs, and virtual instruments. Sequencers allow users to record, edit, and play back MIDI performance data. Popular options include Steinberg Cubase, Ableton Live, and Logic Pro. Notation programs like Finale and Sibelius can transcribe MIDI recordings into musical scores and sheet music. Virtual instruments and effects plugins, known as VST instruments, accept MIDI data as input to generate or process sound. Examples include Native Instruments Kontakt and Arturia virtual analog synthesizers.

Digital audio workstations (DAWs) are designed for audio recording, editing, and mixing, but also provide extensive MIDI recording, editing, and playback capabilities. Most DAWs, such as Avid Pro Tools, Apple Logic Pro, and PreSonus Studio One have MIDI tracks, editing tools, and can host VST instruments. Advanced integration with MIDI controllers is also common. Overall, sophisticated MIDI functionality is available in most modern DAW software.

MIDI Applications

MIDI has three main applications: sequencing, recording, and live performance, controlling synthesizers and other electronic instruments, and automating equipment such as audio, lighting and more.

MIDI sequencing is used heavily in music production (Source) to input and arrange musical ideas digitally using MIDI controllers, keyboards, pads, and other devices. Recording engineers then use MIDI sequence data to send musical performance information to MIDI-compatible synthesizers, samplers, drum machines, and more to generate the actual sounds and record them into an audio track.

Similarly, musicians use MIDI controllers like keyboards and MIDI-enabled guitars both in the studio and live on stage to generate and manipulate synthesizer sounds in real-time. MIDI messages from their instruments are sent to synths, effects, and other gear, enabling dynamic control over a broad palette of electronic sounds.

Beyond instrument and audio control, MIDI protocols can automate lighting, video, and other systems by embedding MIDI show control messages into a MIDI sequence that gets transmitted at the correct timecode during a performance (Source). Many DJ consoles also integrate MIDI to enable effects and performance control.

MIDI File Formats

The most common MIDI file format is the Standard MIDI File (.mid). It contains the sequence of MIDI message data that can be fed to a MIDI-compatible soundcard or hardware synthesizer to produce sound.

Standard MIDI files can store recorder sequencer data and sheet music. They are flexible representations that allow interchanging data between different programs on various platforms. The three main types are:

Type 0 – single track
Type 1 – multiple synchronous tracks
Type 2 – multiple asynchronous tracks

Type 0 is the most compatible, as data can be easily converted to different MIDI sequence formats without losing timing information. Type 1 and 2 files separate different elements like channels, instruments, or musical parts into distinct tracks that may follow independent tempos.

The Future of MIDI

MIDI 2.0 is a new spec currently in development with a goal to build on MIDI 1.0 to expand its functionality and resolution. According to the MIDI Association, “The MIDI 2.0 Protocol replaces RPN and NRPN with 16,384 Registered Controllers and 16,384 Assignable Controller that are as easy to use as Control Change and have 32-bit resolution” (MIDI Association). The MIDI Association notes that MIDI 2.0 will still focus on backward compatibility: “Architectural concepts and semantics remain the same as MIDI 1.0. Compatibility for translation to MIDI 1.0 will be possible” (MIDI 2.0 Spec).

A key benefit will be higher resolution and more controllers that offer artists and musicians finer control over parameters and expressiveness in their work. As noted in Sweetwater Insider, “MIDI 2.0’s main advantages involve smoother workflow and higher resolution for greater expressiveness” (Sweetwater Insider). So while staying backward compatible, MIDI 2.0 has significant potential to expand what’s possible with MIDI technology.