MIDI
MIDI is the language your keyboard, DAW and synths use to talk to each other. It doesn't carry sound at all. It carries instructions: which note, how hard, how long. That's what makes MIDI so easy to edit, and why it's the backbone of almost every modern production.
What is MIDI?
MIDI (Musical Instrument Digital Interface) is a standard way for musical devices to send performance data. It was introduced in 1983 so that synths from different companies could control each other. Today it connects keyboards, drum pads, DAWs, plugins, lighting rigs and even phone apps.
The key idea: MIDI is data, not audio. A MIDI note is like a line in a piece of sheet music. It says "play C4, fairly hard, for half a second". The instrument that receives it (a plugin synth, a sampler, a hardware keyboard) makes the actual sound.
Because MIDI is just instructions, you can change the sound after recording. Played a part on a piano patch? Swap the plugin for strings and the same performance plays strings. You can't do that with a recorded audio file.
Notes, Velocity & Note On/Off
Most MIDI values run from 0 to 127 (128 steps). A played note sends two messages:
- Note On: sent when you press a key. It carries the note number (which key) and the velocity (how hard).
- Note Off: sent when you release the key. The time between Note On and Note Off is the note's length.
What one note looks like as MIDI
Note 60 is middle C. Some software calls it C3 and some calls it C4, but the number is always 60. Each number up is one semitone higher, so note 72 is the C one octave above.
Velocity is how hard (really, how fast) you hit the key. Most synths map it to volume, and many also map it to brightness. A Note On with velocity 0 is treated as a Note Off. Real drummers and pianists never hit every note at exactly the same velocity, so varied velocities are one of the quickest ways to make programmed parts feel human (see Groove & Swing).
Control Change (CC) Messages
CC messages (Control Change) send the position of knobs, faders, wheels and pedals. There are 128 CC numbers (0–127), each carrying a value from 0 to 127. Some numbers have standard jobs:
| CC # | Name | What it usually does |
|---|---|---|
| CC1 | Modulation wheel | Vibrato depth, filter cutoff, or whatever the synth maps it to |
| CC7 | Channel volume | The instrument's overall level |
| CC10 | Pan | Left/right position (64 = center) |
| CC11 | Expression | Volume changes within a performance, such as string swells. Works as a percentage of CC7 |
| CC64 | Sustain pedal | 0–63 = off, 64–127 = on. Holds notes after you release the keys |
For orchestral libraries, set the overall level with CC7 once, then draw your swells and dynamics with CC11 (expression) or CC1 (many libraries use the mod wheel for dynamics). That way you can ride the performance without losing your mix balance.
Pitch bend
Pitch bend has its own message type, separate from CCs, and much higher resolution: 16,384 steps instead of 128. The center value means "no bend". The bend range is set on the synth, not the controller. A range of ±2 semitones is a common default. Lead players often set ±12 for octave dives, and many 808 patterns rely on glide rather than pitch bend.
Other messages
- Aftertouch: pressure on a key after it's down. Channel aftertouch sends one value for the whole keyboard. Polyphonic aftertouch sends one per key (rarer).
- Program Change: tells an instrument to switch presets.
- MIDI Clock: keeps tempos in sync between devices, such as a DAW and a hardware drum machine.
MIDI Channels
One MIDI connection carries 16 channels. Each channel can control a different instrument, like 16 separate lanes on one cable. In a DAW, each MIDI track usually handles its own routing, so channels matter most when you work with hardware or multi-timbral plugins (one plugin playing several instruments).
A common convention: channel 10 is reserved for drums in the General MIDI standard. Many drum machines and older keyboards still default to it.
Editing in the Piano Roll
The piano roll is the DAW editor that shows MIDI notes as bars on a grid: pitch from bottom to top, time from left to right, and a velocity lane underneath. Here you can:
- Draw, delete, move and resize notes.
- Edit velocities by dragging the bars in the velocity lane.
- Draw CC and pitch bend curves in automation lanes.
- Transpose a whole part with one drag, or fix a single wrong note after recording.
Quantize
Quantize snaps notes to the nearest grid line, such as 1/16. It fixes timing mistakes, but 100% quantizing makes everything sound robotic. Better options:
- Strength (or amount): move notes only part of the way, for example 50–75%.
- Swing: push every second 16th note late for a shuffle feel.
- Quantize only the start, not the length, so the feel of held notes stays natural.
- Groove templates: copy the timing of another clip (such as a classic drum break).
Before and after quantize (1/16 grid)
Partial quantize keeps a little of the player's original timing. Use 100% for electronic genres that want machine precision, such as techno.
MIDI Controllers & Mapping
A MIDI controller is hardware that sends MIDI but usually makes no sound itself. Common types:
- Keyboard controllers (25, 49, 61 or 88 keys), often with pads, knobs and faders.
- Pad controllers for finger drumming and launching clips.
- Control surfaces with faders and knobs for mixing.
MIDI mapping links a physical knob to a setting in your DAW or plugin. Most DAWs use a "learn" mode: click the on-screen control, move the hardware knob, and they're linked. Map the controls you touch most, such as filter cutoff, a macro, or a send level.
MPE (MIDI Polyphonic Expression) gives each note its own channel, so every finger can bend pitch, change brightness or add pressure separately. It is used by expressive controllers like the ROLI Seaboard and the Ableton Push 3, and by synths that support MPE.
MIDI vs Audio
| MIDI | Audio | |
|---|---|---|
| What it stores | Instructions (notes, velocity, CCs) | The actual sound wave |
| File size | Tiny (kilobytes) | Large (about 15 MB per stereo minute at 24-bit/44.1 kHz) |
| Change the sound later? | Yes, swap the instrument | Only with processing |
| Fix one wrong note? | Easy, drag it | Hard, needs editing or pitch correction |
| Change tempo | Perfect at any tempo | Needs time-stretching |
| Best for | Synths, drums, virtual instruments | Vocals, guitars, live instruments, samples |
When a MIDI part is finished, many producers bounce (render) it to audio. This saves CPU and commits to a sound so you stop tweaking it.
MIDI 2.0
MIDI 2.0 was adopted in 2020. It keeps compatibility with MIDI 1.0 and adds much higher resolution (velocity and controllers with far more than 128 steps), per-note controls, and two-way communication so devices can describe their own settings to each other. Support is growing in operating systems, DAWs and controllers, but MIDI 1.0 is still what most gear uses day to day.
Recording MIDI
Recording MIDI is like recording audio, but much more forgiving.
- Count-in: turn on a 1-bar count-in and the metronome so you start in time.
- Overdub: record new notes into an existing clip without erasing what's there. Perfect for drums: record the kick on one pass, the snare on the next, then the hats.
- Loop recording: loop a section and record several takes in a row, then pick the best one.
- Capture / retrospective record: many DAWs remember what you played even when you weren't recording [Ableton: Capture MIDI; Logic: Capture as Recording; FL Studio: Dump score log to selected pattern].
- Connect a MIDI keyboard (or turn on your DAW's computer keyboard mode [Ableton: press M; FL Studio: Typing keyboard to piano; Logic: Cmd+K Musical Typing]).
- Create a MIDI track with a drum sampler [Ableton: Drum Rack; FL Studio: FPC; Logic: Drum Machine Designer]. Set the tempo to 90 BPM and enable a 1-bar count-in.
- Loop 2 bars. Turn on overdub [Ableton: MIDI Arrangement Overdub; FL Studio: Overdub recording mode; Logic: Merge in Cycle mode]. Record the kick, then the snare, then the hats in separate passes.
- Open the piano roll. Select all and quantize to 1/16 at about 60% strength.
- Edit velocities: make the hats alternate roughly 100 and 70, and lower a few ghost snares to around 40.
- Record mod wheel (CC1) movement on a synth track while holding a chord, then open the CC1 lane and smooth out the curve.
MIDI stands for Musical Instrument .
Most MIDI values, including velocity, range from 0 to .
The sustain pedal sends CC number , and the mod wheel is CC .
One MIDI connection carries channels.
1. What does a MIDI file actually contain?
- A compressed recording of the performance
- The sound of the synth
- Instructions such as note numbers, velocities and timing
- A list of plugins
MIDI is data, not audio. The receiving instrument creates the sound.
2. Which CC is the standard sustain pedal?
- CC1
- CC7
- CC11
- CC64
CC64 is sustain: values 64–127 mean pedal down, 0–63 mean pedal up.
3. You recorded a piano part via MIDI but want it on strings. What do you do?
- Swap the instrument plugin on the track; the notes stay the same
- Re-record the whole part
- Apply a string EQ preset
- Time-stretch the audio
Because MIDI stores instructions, any instrument can play them back.
4. Why might you quantize at 60% instead of 100%?
- It uses less CPU
- It tightens the timing while keeping some of the human feel
- It changes the notes' pitch
- It makes the notes louder
Partial quantize moves notes only part of the way to the grid, so the groove stays natural.
5. What does overdub do when recording MIDI?
- Deletes the previous take
- Converts MIDI to audio
- Doubles the tempo
- Adds new notes to an existing clip without erasing what's there
Overdub merges each new pass into the clip, so you can build a drum pattern one part at a time.