Micro-tones are notes that are smaller than one half-step apart. If you look at a keyboard, each note is one half-step so we are talking about notes that "fall in between the cracks" on the keyboard.
The human ear can discern them, however, and even hear them as independent notes rather as sharp or flat versions of Western music’s half-step system. Easily. Many cultures use micro-tones. (There’s a case to be
made for Western music using them, too. Some say they fell out of use and others say they are still in use but not acknowledged.)
Middle Eastern music is the most commonly cited example but most other cultures have them somewhere. I have noticed that cultures with vocal music that is somewhat independent from instruments almost always use micro-tones though they aren’t always called that. Think about sean nós singing in Ireland, Blues pitch bends, Native American music and on and on. These “small” notes are often called ornaments or decoration but they are critical to the melody.
Middle Eastern music is the most commonly cited example but most other cultures have them somewhere. I have noticed that cultures with vocal music that is somewhat independent from instruments almost always use micro-tones though they aren’t always called that. Think about sean nós singing in Ireland, Blues pitch bends, Native American music and on and on. These “small” notes are often called ornaments or decoration but they are critical to the melody.
Some instruments can play these notes
easily (are even designed to) and others face a few challenges trying to use them (though there is almost always a way.) Cultures that focused on those micro-tones tend to have more instruments that play them easily. Cultures
that did not pay much attention to the notes "in between" in song tend to have instruments that play notes with more clear cut divisions that make it tricky to get to the micro-tones.
Cultures that did not use much or any notation before Western colonization hit them are more likely to call the micro-tones ornaments or decoration rather than calling them notes that are
part of the tune. And yet, if you leave those “ornaments” out, you are not preforming the music accurately. I am fascinated by how Irish music has taken the grace note system from Western music and started to expand
it to show all those “little” notes that are so critical to this music. Though some say this is too rigid and limits the “ornament” notes. (Mind you, these grace notes and ornaments in
Western music originally represented an improvisation system for Classical music that fell out of use and is only now being revived itself. They weren’t always strict notes but rather suggestions
of places and ways to add something. So you could say they are returning to something like their original use in non-Western music.)
Cultures that used a notation system of their own that incorporated micro-tones kept on calling them notes, not ornaments, even after the Western music notation system got thrown at them.
What’s more, they began adapting the Western notation to show those micro-tones. This is still a work in progress and some say it won’t ever really show those notes properly. But they used to say rhythm couldn’t
be shown by the Western notation at all so it will be interesting to see just how things change.
In all these cases, the Western notation system, which was often forced onto other cultures, is now being changed and expanded by the very music it was meant to replace or "civilize".
My take away from all this is not new. Music doesn’t exist in a vacuum and it crosses boundaries with ease. Language, country, class and notation style. Music is constantly
changing and transforming and each different style or twist creates something beautiful that is worthwhile.
