Sound, Pitch and the Octave

Welcome to the course. Before we open the piano roll and talk about scales or chords, we're going to start with the raw material of everything you produce: sound itself. This first lesson will help you everywhere, when you tune an 808, when you set an EQ or when you double a lead an octave up. Nothing complicated here, just a few very solid ideas that everything else will build on.

Sound is air that vibrates

When your speaker plays a kick, its cone moves forward and back very quickly. It pushes the air, then releases it, and those small changes in pressure travel to your ear, where they make your eardrum vibrate. Every sound, whether it's a voice, a piano or a snare, is a vibration of this kind.

Some vibrations are regular: the same movement repeats, identical, hundreds of times per second. Your ear then hears a precise pitch, a note you could sing. Other vibrations are disordered, like a hi-hat or the hiss of a snare: we call that noise, and you'd have a hard time singing its note. Many sounds mix the two, but this course is mainly about sounds that have a pitch.

Pitch is measured in hertz

Pitch depends on the number of vibrations per second, which we call frequency. It's measured in hertz: a sound at 200 hertz goes back and forth 200 times per second. The more vibrations there are, the higher the sound; the fewer there are, the lower it is. Listen to four very simple sounds, each one faster than the last.

These are sine waves, the purest sounds there are, with no added color. You can hear the pitch rise with each button. The human ear picks up roughly the frequencies between 20 hertz and 20,000 hertz, that is, 20 kilohertz. The upper limit drops with age, and even faster when you're often exposed to loud volumes: that's a good reason to turn your headphones down a little during long sessions.

A 440, the note everyone tunes to

So that all instruments can play together, musicians agreed on a reference note: the first A above middle C on the piano vibrates at 440 hertz. On this site, that note shows up as A4, depending on the software you chose in the settings; we'll see in the next lesson why DAWs don't all give it the same name. Tuners, synths and plugins are almost all set to this A 440 by default.

Both sounds have exactly the same pitch, and yet you don't mix them up. What sets them apart is called timbre, the color of the sound: the piano contains extra frequencies that the sine wave lacks. We'll study this in the lesson on harmonics and timbre. For now, just remember that pitch and timbre are two different things.

Doubling the frequency takes you up an octave

Now let's try a key experiment. We'll start from a sound at 220 hertz, double its frequency to reach 440, then double it again to reach 880. Listen to the three sounds one after another, then to the first two played together.

You probably noticed: the three sounds feel like the same note, higher and higher. And when the first two play together, they blend so well that it's hard to tell them apart. This distance, which you get by doubling the frequency, is called the octave. That's why the three sounds share the same name: they're three A's, in three different octaves.

Going the other way, dividing the frequency by two takes you down an octave. The next table follows A from low to high, with, for each octave, where you'll often run into it in a track.

Look at the frequency column. Between A1 and A2, there are only 55 hertz of difference; between A5 and A6, there are 880. And yet your ear hears the same musical distance, one octave. It doesn't count the hertz being added; it compares ratios. That's why EQs and spectrum analyzers use a special scale, called logarithmic, on which each octave takes up the same width on screen: there's as much room from 50 to 100 hertz as from 5,000 to 10,000 hertz.

Why two A's sound alike

When two sounds are an octave apart, the higher one makes exactly two vibrations while the lower one makes one. Their movements line up again at every cycle, without ever working against each other. There's a second, deeper reason. A musical sound is almost never a single frequency: an A at 220 hertz also contains, more faintly, frequencies at 440, 660, 880 hertz and so on, which we call its harmonics. Now, all the frequencies of an A at 440 hertz are already among those of the A at 220. So the ear hears the high A as part of the low A.

This kinship is so strong that most musical traditions treat two notes an octave apart as one and the same note. In production, you use it all the time. In the next figure, the second bar is an exact copy of the first, one octave higher. Listen: it really is the same melody.

Producers often double a lead an octave above to make it brighter, or a bass an octave below to give it weight. The melody doesn't change; only its place in the low or high range changes. We'll come back to this in the lesson on registers and where each part sits.

The parts of the spectrum you need to know

Producers and sound engineers divide the range of frequencies into broad zones. The exact limits vary from person to person, so treat the numbers in the table as rough guides, not as borders.

Let's connect this to notes. A1, at 55 hertz, is in the sub. C1 vibrates at about 33 hertz and C2 at about 65: an 808 played between these two notes has its fundamental almost entirely in the sub. At the other end, a hi-hat doesn't really have a note, and its energy sits mostly in the highs. Listen to four sine waves, one per zone. On a phone speaker, you'll probably hear almost nothing on the first button, so put on headphones.

The way the sub disappears on small speakers explains a problem you may already have run into: an 808 that sounds huge in headphones and becomes almost inaudible on a phone. In the lesson on the 808 and the sub, we'll see how to make it audible everywhere. For now, get into the habit of linking each note to its frequency, with the next tool.

In the next lesson, we finally open the piano roll: you'll see how these notes are laid out on its keyboard, and why each DAW numbers the octaves its own way.