MIDI: The Language That Controls Digital Instruments
Introduction
MIDI (Musical Instrument Digital Interface) is not audio — it is a digital language that tells instruments what to play, how loud, and how fast. Think of it as sheet music for computers. Since its introduction in 1983, MIDI has become the universal standard for controlling electronic instruments.
What MIDI Actually Sends
When you press a key on a MIDI keyboard, it sends a message like:
Note On: Note = C4 (60), Velocity = 100, Channel = 1
This tells the receiving instrument: “play middle C at velocity 100 on channel 1.” The instrument then generates the actual sound.
MIDI messages contain no audio data — only instructions. This is why MIDI files are tiny compared to audio files.
Core MIDI Message Types
| Message | What It Does | Range |
|---|---|---|
| Note On/Off | Starts and stops a note | Note: 0–127, Velocity: 0–127 |
| Control Change (CC) | Adjusts parameters (volume, pan, filters) | CC# 0–127, Value: 0–127 |
| Program Change | Switches presets or patches | Program: 0–127 |
| Pitch Bend | Bends pitch up or down | Value: 0–16383 (14-bit) |
| Aftertouch | Pressure applied after key is pressed | Value: 0–127 |
| System Exclusive (SysEx) | Manufacturer-specific data | Variable |
Important MIDI CC Numbers
| CC# | Parameter | Common Use |
|---|---|---|
| 1 | Modulation wheel | Vibrato, filter sweep |
| 7 | Volume | Track volume |
| 10 | Pan | Stereo position |
| 11 | Expression | Dynamic volume control |
| 64 | Sustain pedal | Piano sustain |
| 91 | Reverb send | Effect depth |
| 93 | Chorus send | Effect depth |
MIDI Channels
MIDI supports 16 channels, allowing one cable to carry 16 independent instrument parts. In a DAW, each MIDI track is typically assigned to a different channel.
- Channel 1 — often the default for single instruments.
- Channels 10 — traditionally reserved for drums in General MIDI.
- Multiple channels — useful for multi-timbral instruments (e.g., a single synth playing bass on ch.1, pads on ch.2).
MIDI in Your DAW
- MIDI clips — contain note data that you can edit in the piano roll.
- Quantize — snaps notes to the nearest grid subdivision to correct timing.
- Velocity editing — adjust how hard each note is played for dynamic expression.
- MIDI Learn — map a hardware controller knob to any DAW parameter by moving the knob while in learn mode.
MIDI vs. Audio
| Aspect | MIDI | Audio |
|---|---|---|
| Data type | Instructions | Waveform samples |
| File size | Tiny (KB) | Large (MB) |
| Editability | Fully editable (pitch, timing, velocity) | Limited (requires audio processing) |
| Sound source | Needs an instrument to generate sound | Self-contained waveform |
| Quality | Depends on the instrument | Depends on the recording |
Practical Tips
- Use MIDI for composition, audio for recording — they serve different purposes.
- Layer MIDI and audio — trigger a MIDI piano and layer a recorded piano for richer tone.
- Record MIDI in real time rather than drawing notes — it captures human feel and dynamics.
- Export MIDI when collaborating — collaborators can use their own instruments with your note data.
- Back up MIDI files — they are the source code of your composition.
Conclusion
MIDI is the backbone of modern production. Understanding MIDI messages, channels, and CC numbers gives you precise control over every virtual and hardware instrument in your studio.