I am deeply in love with all kinds of music. Actually, I feel deeply sorrowful when someone asks me what my main instrument is. I literally play piano, guitar, bass, harmonica and ukulele. I even have a violin. Obviously, I am not a virtuoso - that is so true. But I am into philosophy of music, and to me, that is what really matters.
When you listen to something - it can be birds singing, leaves rustling; you hear some noises. In the nature, if you lend an ear, you'll notice that they are perfectly in order. You don't feel anything abnormal. That's because music history developed upon the human ear, what was appealing to an ear over centuries evolved into what we call music today.
That is the reason we know seven modes. The most known is Ionian, major tone. For instance, Locrian mode is not feasible to the human ear, it disappeared through something similar to natural selection of music and time. Music is nature. Years after, these harmonies were documented under the name of "music theory". Bach, Vivaldi, Beethoven didn't follow these rules, they looked at the nature. They composed what would be appealing to compose, that's why they shaped music into an art from natural harmonied noises. People documented their works later on.
When you listen to a music, it is bunch of notes in order. You hear D4, proceeding with a note that is higher in frequency. It might be something E? Higher? F? So, the story goes on. Once you have a prototype of the formula you hear, you can play it in anywhere. Play the melody on harp, violin, harmonica, saxophone; it's you that decide. They are some vehicles, notebooks, compilers for music.
Until now, I have taught music theory to ten of my friends. I even wrote a handwritten booklet for a person I love. Yet, I don't have a music of my own. The tragedy is similar to the "centipede" problem. While you ponder about which leg to step with, every other bug has already flown away.