Why Does Music Only Use 12 Notes?

So how comes there are only 12 notes in music? Sure, we can use the same set of notes multiple times, or we can play in between these notes, but how comes we're talking about 12 notes and not 13 or 14? It comes from an idea called tonality, and what that means is that in any piece of music, there'll be one note called the tonic, which is what all the other notes relate back to. If a piece of music is in the key of C, that means that all the other notes are seen as relative to that initial note of C. And this note, the tonic, is kind of like a home for the music. It's often where a piece of music begins, it will then go on a journey using many other notes, and when it comes back to the original tonic, it will feel like the piece has come to a natural ending, and the music has come to its home. For example, let's take the song Twinkle Twinkle Little Star. It's in the key of G major, and it begins on the note G. Then throughout the song, it uses different notes, goes on a little journey, and when it gets to the end, it finishes again on the tonic, G. So we know that other notes are related to this tonic, but how do we work out how many other notes there are, and how closely are these other notes related? So each time we play a note, we're actually hearing more than just the initial note that we think of. For example, if I were to play this E on my guitar and then stop the string, you'll hear the other strings, which are related to this E, ringing out after I've stopped the first string. Now that's because these other notes are harmonics, which means they're very closely related to the note of E. It's not because I'm accidentally knocking the strings. If I were to place my finger, say, on an F and do exactly the same thing, you don't get those other notes ringing out. This is something called the harmonic series, and it applies to all sounds. It doesn't have to be a stringed instrument, and what that means is every time we divide the string or the sound wave into further parts, quarter, a fifth, a sixth, we'll get further notes, and we'll get the next closest related harmonic. So we now know where these related notes come from, but how do we work out what notes they are, and in what order they're related? To do that, we're going to divide the string into equal parts. First of all, let's just play the open string. I'm going to play the A string, and so this is our fundamental note. This is the tonic A. Now what I can do to find the next closest related note is to divide the string in half. If I place my finger halfway and play the string, I get an octave A. So this is the same note, it's A, but it's an octave higher. Okay, now let's do the same thing, but we're going to divide it into three equal parts. So I'm going to place my finger a third of the way along the string, and we get this note, and this note is an E. So the next closest related note to A, other than the octave, is E, and the relationship between these two notes is a fifth. A, B, C, D, E. This relationship between the tonic and the dominant, the first and the fifth, is so powerful in how western music is made up. So much so that if you're playing a piece and you see a dominant seventh chord, like an E7, that alone might be enough to tell you that you're playing in A minor or A major. You don't need to see the key signature or where the music is beginning or ending. So we've taken this note of A, and we've established that the fifth of that note is an E. So what happens if we now play the E string and find out which notes are related to that? So, of course, the first note is going to be E. Halfway along the string, we'll find the octave, another E, and then dividing the string into thirds, we get a B. So B is the dominant of E. We can do the same thing with the B string, octave B, third of the string, gives us an F sharp. So F sharp is the dominant of B. We can keep going with this with every new note that we find, to find out what the dominant is of that particular note. And what will happen is on the 12th time, we'll end up playing the D string, and we'll try to find out the dominant of that, and we'll get an A. So we'll be back where we started after 12 times. So there we go. There are 12 notes in music because of that very important, but natural relationship between the first and the fifth. Now it's worth saying at this point that this is very much a generalization and a basic overview of how we develop our fundamentals of music. There are many other cultures and styles that use different systems to find their notes, but generally speaking, most music that you listen to, popular, classical, or jazz, will use the same 12 notes. This doesn't mean that it's wrong to use other notes or notes between the notes. This is just a basic overview on how we develop our system of naming notes. Thanks very much for watching. Don't forget to subscribe and check out my other videos.