Introduction to MIDI
What Is MIDI?
MIDI stands for Musical Instrument Digital Interface, but despite the technical name, the idea behind MIDI is very simple.
MIDI is a way for musical devices to talk to each other.
Instead of sending sound, MIDI sends instructions. These instructions describe musical actions such as playing a note, changing a sound, moving a knob, or starting a song. The receiving device then decides how to turn those instructions into sound or behavior.
You can think of MIDI as a musical language, not an audio signal.
What MIDI Is Used For
MIDI is used whenever:
- a keyboard plays a synthesizer
- a controller adjusts a parameter
- a sequencer records and plays music
- multiple devices need to stay in time
MIDI allows one device to control another, even if they are very different internally.
A Simple Way to Think About MIDI
Imagine a conductor giving instructions to musicians.
The conductor does not produce sound.
Instead, they tell musicians what to do.
MIDI works the same way:
- one device sends instructions
- another device performs them
MIDI Channels
MIDI uses the idea of channels to organize communication.
There are 16 MIDI channels, and each channel can be thought of as a separate musical “lane”.
One MIDI connection can carry messages for many instruments at once by placing them on different channels.
For example:
- Channel 1: piano
- Channel 2: bass
- Channel 10: drums
A device usually listens only to the channels it is assigned to.
Channel Messages
Most everyday MIDI messages are channel messages.
Channel messages:
- are sent on a specific MIDI channel
- affect only the instrument or part listening on that channel
You can think of channel messages as saying:
“To the instrument on this channel: do this.”
Note Messages
Note messages tell a device which note to play and how.
They describe:
- which note was pressed
- how strongly it was pressed
- when it was released
These messages form the basis of melodies, chords, and rhythms.
Control Messages
Control messages describe changes to parameters.
They are used for:
- knobs and sliders
- pedals
- switches
- expressive performance control
Control messages allow sounds to be shaped and changed in real time.
Program Change Messages
Program Change messages tell a device to switch sounds.
They are commonly used to:
- change presets
- select instruments
- recall configurations
They allow performers to move quickly between different sounds.
Messages That Are Not Tied to Channels
Not all MIDI messages belong to a channel.
Some messages affect the entire system, not a single instrument.
These are called system messages.
System Common Messages
System Common messages are used for coordination between devices.
They often deal with:
- synchronization
- identification
- data exchange
They apply to the whole MIDI system rather than to one channel.
System Real-Time Messages
System Real-Time messages are about timing and transport control.
They are used to:
- keep devices synchronized
- start and stop playback
- maintain steady timing
These messages are very short and very urgent. They are processed immediately so that timing stays accurate.
System Exclusive (SysEx)
System Exclusive, or SysEx, messages are used for device-specific communication.
They allow manufacturers to:
- expose advanced features
- configure devices
- transfer presets and settings
SysEx messages are like private conversations that only the intended devices understand.
Why MIDI Has Different Message Types
MIDI includes many message types because musical communication involves many different tasks:
- playing notes
- controlling parameters
- synchronizing time
- configuring devices
Each message type exists to serve one of these roles clearly and efficiently.
Why MIDI Has Lasted So Long
MIDI has been used for decades because it is:
- simple
- reliable
- flexible
- widely supported
Even modern music systems still rely on the same core MIDI ideas.
What Comes Next
Once you understand:
- that MIDI sends instructions, not sound
- that channels organize communication
- that different messages have different roles
you are ready to explore how MIDI works internally.
Everything that follows—bytes, bits, SysEx, masking, and advanced control—exists to support these simple concepts.
Summary
MIDI is a communication protocol that allows musical devices to exchange instructions. It uses channels to organize messages, includes both channel-specific and system-wide messages, and supports performance, control, timing, and configuration. Understanding MIDI at this conceptual level prepares you for learning its technical details with confidence.