MIDI (Musical Instrument Digital Interface) is a protocol that allows computers, musical instruments and hardware to communicate via a series of messages.
What is MIDI? It all began in the 80s
Back in the late 70s/early 80s, synthesizers began to become more prominent in music. As more manufacturers jumped on board with this and decided to produce their own electronic instruments, it became evident that there needed to be some kind of standard in place between manufacturers for the sake of compatibility.
Dave Smith of Sequential Circuits and Ikutaru Kakehashi of Roland were amongst the first to start circulating the idea.
In 1981, Dave Smith and Chet Wood developed and proposed the concept of the Universal Synthesizer Interface to the Audio Engineering Society. Over the following months, the standard was modified and developed further with input by other manufacturers.
After some back-and-forth about the name, they settled on MIDI (Musical Instrument Digital Interface), and the first finalized standard of the format was announced in 1982 and made its first appearance on the Sequential Circuits Prophet 600 by December 1982. Roland’s Jupiter-6 soon followed suit.
At the January 1983 NAMM show, these two synths were successfully MIDI-synched, blowing the doors of possibility wide open for musicians everywhere. Could you imagine having been in that room?!
So how does MIDI work?
The first important point to realise is that MIDI has no sound. What is MIDI? It is a set of instructions, not an instrument.
It works by sending and receiving instructions between devices via MIDI messages over MIDI channels. Let’s break this down.
This is the data that instructs a device on what to play, when to play and how to play it.
For example, if you are using a keyboard connected to a computer via a MIDI port (more on this later), that keyboard is transmitting information corresponding to what you are playing via MIDI messages to the computer.
These transmitted MIDI messages can include:
- Note on/Note off – which notes are triggered (i.e which keys are struck), and when they are released
- Velocity – how hard or soft the keys are pressed initially
- Aftertouch – pressure applied after initial velocity as the note is sustained
- Pitch Bend – many keyboards have a “pitch wheel” that can bend a note up or down a specified amount
- Modulation – many keyboards also feature a “mod wheel” that can be programmed to perform a variety of functions, but often by default introduces a pitch modulation or vibrato to a sound (much like a singer might do with their voice).
- Panning – where the sound sits in the stereo field from left to right
…and much more. In fact, this list barely scratches the surface!
The computer can record all of these messages via a MIDI sequencer, which can be played back, easily modified or edited and saved as a MIDI file.
MIDI channels are what MIDI messages are transmitted across.
Each MIDI device can have up to 16 MIDI channels, with each channel representing an instrument. Each track in your MIDI sequencer transmits to one instrument over one channel.
Let’s say you are transmitting from your computer to an external sound module. An example layout could be:
- Channel 1: Piano
- Channel 2: Bass
- Channel 3: Synth Pad
- Channel 4: Guitar
…and so on, up to 16 channels for that particular device.
What is MIDI sequencing?
The MIDI sequencer is where all MIDI data is arranged across a timeline for playback. If you are recording MIDI, this is where you will see your recorded notes and movements appear,
Introducing the Pianola: The proto-MIDI sequencer
Pianolas (a.k.a “Player Pianos”) are those pianos you may have seen in the movies that seemingly play on their own.
The ‘songs’ that Pianolas play are transcribed onto a particular roll of paper with a series of holes punched into it, known as “Piano Rolls”. The placement of these holes correspond with the notes of the song.
The piano rolls are placed into a mechanism inside the Pianola that is connected to the piano keys. On playback, the mechanism rotates. As it does, the holes in the piano roll trigger the corresponding piano keys via the mechanism.
The piano roll is basically the same principle as a MIDI file. It makes no sound on it’s own, but contains all the information to tell the instrument what to play.
What is MIDI Hardware?
With the processing power of modern day computers, DAWs (Digital Audio Workstations) and VSTs (Virtual Studio Technology), we are a lot less reliant on external MIDI hardware than we once were.
That doesn’t mean MIDI hardware is obsolete by any means.
Being its own protocol separate from audio, MIDI requires its own specific connections to connect devices.
Most MIDI-capable hardware devices feature MIDI ports to transmit and receive MIDI messages. These ports act as the ‘mouths’ and ‘ears’ of these devices.
Here’s what they do.
- MIDI in: This is where the device receives MIDI messages
- MIDI out: This is where the device sends MIDI messages
- MIDI thru: Sends a copy of received MIDI data
MIDI thru isn’t always available on every instrument. When it is, it’s used to daisy-chaining instruments that you want to keep in sync.
MIDI ports require specific cables that are capable of transmitting MIDI data. These MIDI cables are recognizable by their 5-pin connectors.
MIDI can only travel in one direction. If you want a device to both send and receive, you will need 2 MIDI cables.
USB and MIDI
The introduction of USB and it’s ability to send and receive MIDI messages has brought many advantages to the world of MIDI connectivity. For example:
- USB is multidirectional. Unlike standard MIDI cables, USB can simultaneously transmit and receive MIDI, eliminating the need for more than one cable.
- USB has a higher bandwidth. Where a MIDI cable can support up to 16 channels, a USB cable can support 16 virtual MIDI ports, with 16 channels EACH. That’s potentially 256 MIDI channels!
- USB can power devices. Laptop, MIDI controller, USB cable. That’s a mobile studio right there.
Advantages of MIDI
Even though MIDI and audio have completely different purposes, MIDI can have huge advantages over audio in areas where they might overlap, such as recording.
Say, for instance, you’re laying down a track with your favorite keyboard. Sure, you can go ahead and record that part directly to audio – much like you would with vocals or an acoustic instrument. But what happens if you find a better sound to use?
You’d have to re-record the entire track again with the new sound, and hope you nail it too. What happens if you find an even better sound than the second one? This process could go on for hours.
If, on the other hand, you chose to record the MIDI data instead, you could:
Experiment with different presets or sounds while the MIDI data is playing back. Who knows, that piano line might sound better as a guitar, or a synth lead…or could even inspire a totally off-the-wall drum pattern!
Easily edit or quanitise any part of it. What if you’ve recorded straight to audio and it was a great performance with the exception of a couple of parts? You could try to re-record them and splice them into the main track, but it’s highly likely that it will be noticeably different.
Things like the tail of sounds cutting off abruptly where you edit in your re-recorded section, or an audible ‘pop’ where the spliced in audio is out of phase with the original take etc.
This doesn’t happen with MIDI, because editing MIDI is editing the data that is sent to the synth, not the recording of it.
Save processing power for other tasks. MIDI files are absolutely tiny and require barely any processing power for your CPU.
Using track after track of audio inevitably means that at some point your CPU will reach its limit trying to process them all, and glitch out or even freeze up altogether.
What is MIDI? A revolution for electronic instruments
So I hope that gives you a deeper understanding of MIDI, what it’s done for electronic instruments and the role it plays in the studio.
Speaking of the studio, if you’re reading this in preparation to set up a home studio of your own, check out my guide to setting up a home recording studio.