What Is a MIDI Note?

Up to now, we've talked about notes as rows on a grid. It's time to look at what your DAW actually records when you draw a note in the piano roll. The answer often surprises people: it doesn't record any sound. It records an instruction, and that's exactly what makes MIDI so flexible.

A score, not a recording

MIDI, short for Musical Instrument Digital Interface, is a language created in the early 1980s so that electronic instruments and computers could talk to each other. A MIDI note is like a very precise line of a score: it says which key to play, how hard, when and for how long. It's the instrument receiving it, a synth, a sampler or a plugin, that makes the sound.

The very name piano roll comes from there. The player pianos of the early twentieth century read long rolls of punched paper: each hole told the piano which key to press and for how long. Your piano roll is a direct descendant of those rolls. Here's a short melody drawn on the grid.

These six rectangles contain no sound. Send them to four different instruments, and you get four very different results, without touching a single note.

That's the great strength of MIDI: you can change instruments at any time, fix a note, change the tempo or transpose a whole part without playing anything again. An audio recording, on the other hand, freezes the sound: to change a note, you have to record it again or rework it.

What a note contains

Each MIDI note carries a small amount of information. Here it is, in the order you meet it in the piano roll.

• The note number says which key is played. It runs from 0 to 127, middle C is number 60, and each half step adds or subtracts 1.
• The velocity says how hard the key is struck, on a scale that goes up to 127. The instrument usually uses it to set the note's volume, and sometimes its brightness.
• The start says when the note begins, counted in bars, beats and fractions of a beat, not in seconds.
• The length says how long the key stays held down.
• The channel, numbered 1 to 16, says which instrument the note is meant for when several instruments receive the same messages.

In a project on a computer, each track usually sends its notes straight to its own instrument, so you'll hardly ever need to worry about the channel; it's mostly used with external hardware. The note number, on the other hand, is a key's true identity. Octave names change from one DAW to another, as we've seen, but the number never changes.

With 128 numbers, MIDI covers more than ten and a half octaves, far more than the 88 keys of a piano, which run from number 21 to number 108. Number 36 deserves a word: in the General MIDI standard, it's the bass drum, 38 is the snare drum and 42 is the closed hi-hat. That's why many software drum machines put their first pad, often the kick, on that key.

Finally, pitch bend isn't a note: it's a separate message that slides the pitch smoothly, like the wheel you find on the left of many MIDI keyboards.

Velocity, how hard you strike

Velocity comes from the piano: the faster you strike the key, the louder the note. In your DAW, it usually appears in a lane below the piano roll, with one bar per note; some DAWs show it as a percentage rather than on the 0 to 127 scale. Listen to the same hi-hat played at three different velocities.

Without changing a single note, velocity makes the line breathe. A part where every note has the same velocity often sounds mechanical; we'll see how to work with accents in the part on rhythm.

Quantizing: lining the notes up on the grid

When you play on a MIDI keyboard, your notes almost always land a little before or a little after the grid lines. Quantizing, or quantize as DAWs call it, moves the start of each note to the nearest grid line. Here's a phrase played by hand first.

And here's the same phrase after quantizing to sixteenth notes, that is, to the smallest division of this grid.

Quantizing fixes small inaccuracies, but it can also make a part too stiff. That's why many DAWs offer partial quantizing, which pulls the notes toward the grid without snapping them all the way onto it. Here, the lengths have been rounded too, which some DAWs only do if you ask.

Exporting, importing, and what a MIDI pack contains

A MIDI part can leave your project as a file, with the .mid extension. That file contains the notes, their velocities, their starts and their lengths, and often the tempo, but neither the sound of your synth nor its settings. The other way round, dragging a .mid file into your DAW creates a part that any instrument can play.

A MIDI pack is nothing more than a collection of these files: chord progressions, melodies, bass lines, sometimes drum patterns, often with the key and tempo in the file name. They contain no sound: you choose the instrument. And unlike an audio loop, a MIDI loop follows your project's tempo with no processing at all, because it's written in beats and bars.

So a MIDI pack is a starting point, not a finished track. This course will give you exactly what you need to read what's inside: which chords, in which key, with which bass, and how to change them so the result becomes yours.

There's one skill left to pick up in this part: finding on the grid a note you've heard. That's the subject of the last lesson.