What is a MIDI file?

The MIDI format: the DNA of music

A MIDI sequence is a digital file containing music control information, such as notes played, velocity, tempo changes and channel change control commands.

This information can be used to play music on a MIDI instrument, or to record and edit music on a computer.

MIDI files can be read by many music software programs, and are often used for composing and producing electronic music. The information contained in a MIDI file (called "events") is sent from a transmitter (software / sequencer/ DAW, keyboard, pad etc.) to a sound generator (VST plugin, AU, keyboard, arranger, etc.).

MIDIs contain the following information (among others):

Who's playing?
At what tempo?
With what tone?
At what time?
With which notes and how?
And for how long?

So let's open a MIDI file (.mid or .kar) and look at a few lines of these famous "instructions" or "events".

They are displayed here from DAW LOGIC PRO for Mac

What do these lines from track 2 (Piano) tell us?

1 2 1 67 Program 2 ÷ 0 Grand Piano
       1 2 1 99 Control 2 7 100 Volume
       1 2 1 131 Control 2 10 44 Pan
       1 2 1 163 Command 2 11 127 Expression
       1 2 1 195 Command 2 64 127 Sustain
       1 2 2 115 Control 2 91 62 Reverb
       1 2 2 147 Command 2 93 8 Chorus Send Level
       2 4 4 65 Note 2 E3 70 0 0 1 154

       2 4 4 137 Note 2 G3 81 0 0 1 158

       2 4 4 191 Note 2 C4 80 0 0 1 124

       2 4 4 237 Grade 2 E4 87 0 0 1 72

       3 2 4 125 Order 2 64 0 Sustain
 

How are they interpreted?

It's simply a sequence of instructions that run line by line in all dedicated software and hardware: Cubase, Logic, Live!, Korg, Yamaha, Roland, Arturia, Musescore, Reason, GuitarPro, Adobe and more.

Thousands of pieces of information can be listed, from notes to volume and velocity indications, and even more "complex" parameters such as effects settings, or specific to the hardware you're using.

How are they "transported"?

MIDI sequences "circulate" via a physical MIDI cable (via MIDI IN and OUT sockets or USB socket) or virtual connection (an instrument plug-in integrated into the music software, for example).
This musical network complies with the "MIDI standard".

How are they "created"?

MIDI sequences are transcriptions made using specific software that can export .mid files (DAWs), such as Cubase, Logic and Ableton Live!
What are the differences between a MIDI file and an audio file?
A MIDI file and an audio file are two different types of file used to store and play back music. The main differences between them are as follows:
File format: MIDI files use a specific file format that stores music-related data such as notes, control signals and synchronization information. Audio files, on the other hand, store recorded sounds, such as music, lyrics or sound effects.

Sound quality: Audio files are a recording of sound, and therefore have a high sound quality. MIDI files, on the other hand, do not store the actual sound recordings, but only the instructions for playing the music. The sound quality of a MIDI file depends on the device or software used to play it.
File size: As MIDI files do not contain actual sound recordings, they are much smaller than audio files. They are therefore more easily transportable and useful for applications such as mobile music production.
Editing capabilities: MIDI files are editable, allowing you to modify notes, tempo, pitch and other elements of the song. Audio files, on the other hand, are generally more difficult to edit, as they are sound recordings containing only frequencies.
Compatibility: MIDI files are compatible with a wide range of music composition and editing devices and software, while audio files may require specific software or hardware to play.

The active performance of a piece of music on a MIDI-compatible instrument can be recorded on a computer by a sequencer program (or DAW) and stored as a file (MIDI file). MIDI files contain sequences of events, each of which is time-stamped.

A MIDI file thus contains all the information needed to reproduce the same performance at a later date. The MIDI file format was defined in 1988 under the names Standard MIDI-File Format 0 (SMF0) and Standard MIDI-File Format 1 (SMF1). MIDI format 0 files contain a single sequence (track) of MIDI events, while format 1 files contain several, each with an independent time count. The SMF2 format, little used today, is based on format 1.

In addition to events transmitted via MIDI, MIDI files can contain events that contain other information: these are called "meta events". Examples of such meta-events are measure, key, tempo, copyright and song lyrics. Manufacturers also have the option of introducing their own Meta Events, which are then only used on their instruments and are therefore not standard.

Sequencers allow you to insert and edit all events contained in MIDI files, including standard Meta Events. For editing manufacturer-specific Meta Events, there was the XG Works sequencer, which is no longer available. It has been replaced by a number of software tools programmed by MIDI file manufacturers and users.

Today's keyboards often allow you to record your own playing directly as a MIDI file. This eliminates the need to install additional software, and the need for a sequencer in the first instance. Another advantage is that meta-events can also be saved in the file. Keyboards generally have additional functions for editing MIDI files.

With a maximum of 16 MIDI channels, 16 different voices (instruments) can be played simultaneously, independently of each other. On each channel, several sounds (e.g. chords) can be played simultaneously. The maximum total number of sounds that can be played simultaneously is called polyphony. On today's keyboards, however, complex voices load several polyphony values per note. These instruments generally have a polyphony of up to 128 or more.
MIDI files are very useful for music production, as they enable musical information to be stored and manipulated as digital data. Here are some ideas for using MIDI files:
Musical composition: MIDI files can be used to create musical pieces using MIDI composition software such as Ableton Live, Logic Pro X, or FL Studio. MIDI files can be used to create tracks for drums, bass, synthesizer, piano and more.

Synchronization with virtual instruments: MIDI files can be used to synchronize virtual instruments with audio tracks or other MIDI files. This enables virtual instruments to be played from the MIDI track, or instruments used in a song to be replaced by others.
Performance editing: MIDI files let you manipulate recorded performances by modifying the pitch, duration and velocity of notes. This allows you to correct errors or create variations on an existing performance.
Arrangement: MIDI files can be used to create arrangements by modifying the order of sections in a song, or by adding or removing parts.
Live performance: MIDI files can be used to control virtual instruments or live sound equipment, such as samplers, synthesizers or effects.

Music education: MIDI files can be used to teach music by allowing students to visualize notes and chords played on a virtual keyboard, or by using music education software.

GM, GS, XG standards: a universal instrument library

The MIDI sequences we offer are all GM: General MIDI. This means they will play with the right instruments, whatever the software or hardware used. The other two standards are more extensive instrument libraries published by Yamaha (XG) and Roland (GS).

MIDI was developed by Dave Smith in 1981 and introduced in 1983. Shortly afterwards, the first MIDI-compatible instruments were developed by various manufacturers. Since, at the time, MIDI protocol did not yet define the parameters to be used to control special voices, such as bass or violins, or sound effects, it was virtually impossible to couple instruments from different manufacturers.
This problem was solved with the adoption of the General MIDI (GM) standard in 1991, which defined a list of 128 instruments and their program numbers.

Some manufacturers soon realized that limiting GM to 128 programs was not enough, and that effects control needed to be extended to the 128 types of control events also possible.

As early as 1991, Roland extended the GM standard with the GS (General Sound) format, which has already overcome many of GM's limitations.
In 1994, Yamaha introduced the XG (Extended General MIDI) format, which is fully backward-compatible with GM, but offers many more extensions.
Songs created under XG or GS can be reproduced on GM instruments, with certain qualitative restrictions. Similarly, GM songs can also be played on XG or GS. However, XG and GS are not compatible with each other.

GM was extended in 1999 by the inter-manufacturer agreement GM2 (General MIDI 2). GM2 is, like GM, a minimum standard, but it doesn't seem to have caught on completely, as manufacturers Yamaha and Roland still have more possibilities with XG and GS.

Laurent WALKER-HAVETTE