Musical Instrument Digital Interface (MIDI): Meaning, Facts & More

MIDI (Musical Instrument Digital Interface) 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 was first developed in the early 1980s to standardize the growing amount of digital music hardware at the time.

The main purpose of MIDI is to allow different digital musical devices to communicate with each other. For example, a MIDI keyboard controller can send musical performance data to a digital audio workstation like Ableton Live. This data can include note on/off messages, control signals for parameters like volume or vibrato, program change messages and more. The receiving device can then interpret this MIDI data to trigger notes, change sounds, and control aspects of the performance.

At a basic level, MIDI works by allowing devices to transmit and receive event messages that correspond to musical concepts like notes, pitch bends, clock signals and more. This messaging system, along with the physical MIDI cables and ports that connect devices, form the core components that enable the wide compatibility and interoperability that MIDI provides.

How MIDI Works

MIDI stands for Musical Instrument Digital Interface. It is a technical standard that describes a protocol, digital interface, and electrical connectors that connect a wide variety of electronic musical instruments, computers, and related audio devices for playing, editing and recording music (

The key to MIDI is that it is a communication standard. MIDI itself does not make sound, but enables electronic music instruments and devices to communicate with each other by transmitting real-time performance data and commands such as notation, pitch, tempo, vibrato, panning, cues, and clock signals ( This allows MIDI devices to be connected through simple unidirectional MIDI cables, creating a network where a MIDI controller can trigger sounds on a MIDI synthesizer, and MIDI data can be recorded, edited, and played back using a MIDI sequencer or computer.

The transmission of MIDI messages happens via MIDI cables. Standard MIDI cables have 5-pin DIN connectors on each end and transmit MIDI messages one way through 16 channels. This allows up to 16 different devices to communicate along one cable daisy chain. Opto-isolators keep MIDI devices electrically separated, avoiding ground loop and interference issues (

MIDI messages are instructions for musical notes, controllers, parameters, cues, clock signals and other data. The most common MIDI messages include:

  • Note On/Off – Triggers a note to start/stop.
  • Control Change – Alters sound parameters like volume or panning.
  • Program Change – Selects instrument sound patches.
  • Pitch Bend – Bends pitch up or down.

MIDI channels allow for simultaneous transmission of different MIDI data over a single cable. There are 16 available channels, numbered 1-16. This enables independent control of different instruments or parameters simultaneously. MIDI channels create a networking effect where devices can communicate selectively.

Types of MIDI Messages

There are several common types of MIDI messages that are used to control musical instruments and audio hardware:

Note On/Note Off

Note on and note off messages are used to trigger and release notes. The note on message indicates which note to play and the velocity (loudness). The note off message tells the instrument when to stop playing the note. This allows MIDI to simulate the playing of musical notes (Source 1).

Controller Changes

Controller change messages allow adjustment of parameters like volume, pan, sustain pedal, etc. This gives dynamic, real-time control over the performance (Source 2).

Program Change

Program change messages allow selecting different instrument sounds or patches. This lets MIDI access the full capability of advanced synthesizers (Source 3).

Pitch Bend

Pitch bend messages allow subtle control of pitch for realistic musical expression and vibrato effects.

System Exclusive

System exclusive messages contain proprietary data for accessing advanced features of MIDI devices. This allows deep control of sounds and parameters.

MIDI Channels

MIDI allows for communication on up to 16 different channels. Devices can be set to transmit and receive on specific channels in order to prevent multiple instruments from responding to the same message. There are three modes that determine how MIDI channels operate:

Omni Mode – In omni mode, a device receives MIDI messages from all 16 channels. This allows multiple instruments to be controlled from one MIDI controller. However, it means all instruments will respond to any incoming MIDI messages.1

Mono Mode – In mono mode, a device only receives messages from one MIDI channel, ignoring all others. This allows each instrument to have its own channel and prevents multiple instruments from responding to the same messages. However, it requires assigning each device to its own channel.2

Poly Mode – Poly mode is like omni mode in that a device responds to all channels. However, voices are assigned to channels in a round-robin fashion to prevent multiple voices from responding to the same note-on message. This allows polyphonic instruments to be used with multiple MIDI channels.3

MIDI Cables and Connectors

MIDI devices are connected using special cables that have 5-pin DIN connectors on each end. The 5 pins allow transmission of the MIDI data messages between devices.

There are a few types of MIDI cables available:

  • Standard MIDI cables – These typically have 5-pin DIN connectors on each end and come in various lengths like 3 feet, 6 feet, 10 feet etc. They are used to connect MIDI devices like keyboards, drum machines, synthesizers etc. Most MIDI cables have male connectors on both ends.
  • MIDI thru boxes – These allow multiple MIDI devices to be connected together by splitting the MIDI signal.
  • MIDI patch bays – These allow routing of MIDI signals between different devices and aid in setting up more complex MIDI systems.

When shopping for MIDI cables, it’s important to verify they have the proper 5-pin DIN connectors. The connectors should be sturdy and well constructed to withstand wear and tear. Shielded cables help prevent interference. Standard MIDI cable lengths are sufficient for most needs, but longer cables (20 feet +) may require an active booster to maintain signal integrity.


MIDI Devices

There are several common types of MIDI devices used in music production and performance:

Sound Modules/Tone Generators

Sound modules or tone generators are devices that contain synthesized sounds and allow control of these sounds through MIDI. Popular examples include drum machines like the Roland TR-808 and synth sound modules like the Yamaha DX7. Sound modules receive MIDI note on/off messages to trigger sounds and respond to MIDI continuous controller messages to modulate sound parameters like volume, panning, filter cutoff, etc. (Music Tech Alliance)

Keyboard Controllers

Keyboard controllers are devices with piano-style keyboards that play sounds from an external tone generator. They convert key presses into MIDI note on/off messages and other user controls like pitch bend or modulation wheels into MIDI continuous controller messages. Keyboard controllers allow real-time performance and expression using an interface like a piano. Popular options include MIDI keyboard controllers from companies like Akai Professional, Native Instruments, and Arturia.


Digital audio workstations (DAWs) and MIDI sequencers allow users to edit and arrange MIDI information over time. They record and playback MIDI note events, controller messages and other sequencing data. Common DAWs like Ableton Live, Logic Pro, and FL Studio have powerful MIDI sequencing capabilities. Standalone hardware sequencers like classic drum machines also sequence and record MIDI information. MIDI sequencer devices and software are used to compose, edit, and arrange MIDI-based music.(Wikipedia)

Benefits of Using MIDI

One of the main benefits of using MIDI is the ability to play multiple instruments from one controller (Landr). With a MIDI keyboard or other controller, you can play notes and control parameters for synth modules or software instruments in a DAW. This makes layering and blending sounds very easy. It also allows performing one part live while another plays back from the sequencer.

Another major advantage of MIDI is compatibility between different devices and programs (MIDI Association). As long as a piece of gear or software can send and receive MIDI messages, it can communicate regardless of manufacturer or platform. This facilitates connecting keyboards, drum machines, samplers, and more to create complex setups.

Finally, MIDI data is easy to edit and quantize after recording (Producer’s Society). With MIDI, you can tighten up the timing of a performance or even alter individual notes. This allows improving parts without having to re-record them. MIDI data can also be easily transposed or have its velocities or other parameters tweaked globally.

Limitations of MIDI

Although MIDI revolutionized music production, it does have some limitations worth noting (Eimear Clarke):

– MIDI data consists of control messages rather than actual audio signals. This means MIDI instruments and devices may not sound as realistic as real acoustic instruments. The quality of the sound is limited by the device’s onboard sounds and samples.

– There can be latency issues with MIDI, meaning a noticeable delay between pressing a key and hearing the sound. This is because the MIDI data has to be transmitted, interpreted, and triggered. Latency makes it harder to play MIDI instruments in real-time.

– MIDI devices are heavily dependent on hardware components. The MIDI cables and ports have to be compatible between devices. As technology changes, older MIDI gear can become obsolete and lose compatibility with new equipment (Producers Society).

Notable Uses of MIDI in Music

Since its inception in the early 1980s, MIDI has been widely adopted and used in countless musical recordings. Here are some notable examples of innovative uses of MIDI in famous songs and albums:

The 1985 album Hounds of Love by Kate Bush made innovative use of MIDI and sampling technology. The album’s title track used an E-mu Emulator II sampler with MIDI synchronization for the layered keyboard and percussion parts 1.

Depeche Mode’s 1990 hit song “Enjoy the Silence” featured a driving MIDI bassline and string accompaniment created using a Roland D-50 synthesizer. This gave the song a distinct electronic yet orchestral sound 2.

The early 1990s Eurodance act La Bouche used the MIDI standard extensively in their production. Their 1995 album Sweet Dreams layered synthesizers, drums, bass, and other instruments via MIDI sequencing 3.

MIDI was also pivotal in the rise of Chicago house music, Detroit techno, and other electronic dance genres by allowing producers to layer synths, drums, and samples. Pioneering artists like Juan Atkins and Derrick May used MIDI gear like the Roland TR-808 drum machine 1.

The Future of MIDI

MIDI technology continues to advance to meet the evolving needs of musicians and audio professionals. Two major developments that will shape the future of MIDI are MIDI 2.0 and the Web MIDI API.

MIDI 2.0 is the next generation MIDI specification that offers increased resolution, more expressiveness, and tighter timing. MIDI 2.0 supports 32,768 discrete values per knob movement compared to 128 values in legacy MIDI 1.0. This expanded resolution allows for far greater subtlety and nuance when controlling parameters. MIDI 2.0 also introduces profiles that optimize MIDI messages for different use cases like lighting, live performance, and embedded applications (

The Web MIDI API allows web browsers to connect directly to MIDI devices. This enables musicians to use MIDI controllers and instruments through web apps and sites. The Web MIDI API opens up many new possibilities for music creation and collaboration online by connecting MIDI gear to the browser ( For example, musicians could jam together and share MIDI data through a web-based digital audio workstation.

As computing continues to advance, mobile devices and computers will likely take on a greater role alongside traditional MIDI instruments and controllers. Musicians already use tablets and smartphones as portable MIDI gear for controlling synths and sequencers. Future integration of MIDI with mobile and the internet will further enhance the connectivity and convenience that MIDI provides.

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