Every unit in physics are defined such a way they are exactly precise and non-changeable. I highly doubt that music uses note frequencies randomly in the way that comes from heart.
Can someone explain it to me?
In: Technology
Music is based on relative frequencies.
A note that’s one octave higher is exactly twice the frequency of the other note. That’s purely based on physics, and it’s not arbitrary – mathematically, a waveform that’s periodic with frequency 2*f* is also going to be periodic with frequency *f*, so it makes sense that they “sound” like the same note, not a different note.
Other notes in the scale are based on mathematical ratios. What we call a “perfect fifth” is a 3:2 ratio of frequencies. Most harmonies that have been independently discovered by many cultures are simple ratios of frequencies like that.
However, most advanced music has a lot of arbitrary elements too. Western music divides the scale up into 12 equal parts. Dividing by 12 gives you notes that correspond reasonably well to many simple frequency ratios (though not perfectly), but also gives you the ability to “module” to different musical keys and add a lot of complexity that way. But at various times in history this was not popular, and using “pure” frequency ratios was actually preferred. Other cultures divide up the octave into a different number of notes – more or fewer.
Back to your original question, though: while the ratios have an important basis in physics, it’s completely arbitrary that we call a particular note a particular frequency. Most people can’t even tell the difference if you play a song at a slightly higher or lower frequency. (Those that can tell have “perfect pitch”.)
At some point in Western music history, it was decided that A=440Hz. Before then it wasn’t standardized. But it’s completely arbitrary.
In Western music, the notes are based on ratios of pitch frequencies. If you take two frequencies, and one is exactly double the other one, we call those frequencies one octave apart. So it makes them the same note.
We then divide the octave into 12 evenly-sized intervals. Since the ratio of 1 octave is a factor of 2, that means the ratio of each interval is 2^1/12
This gives us certain very pleasing ratios, like the perfect fifth, 2^7/12 – which is very nearly 1.5. A 3:2 ratio of frequencies just “sounds right” to the human ear.
Really, it’s all mathematics. We’ve been using these same ratios since the ancient Greeks.
Up until recently there was a lot of leeway between the actual frequency. Some symphonies were sharper or flatter than others. It had to do with the materials being used and the instruments being made. Since microtonal music has always existed in non-western music, and I. The early-mid 20th century states being incorporated into western, essentially there never really was a strict rule, or it was a brief period during the late 19th century.
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