An interesting question. You must be an engineer or a computer scientist to
want to know these things. I had the same questions when I got started. I
am no expert but many of these things were figured out hundred of centuries
ago. The answer to most things is because it worked, although other systems
would have worked too. A lot of it is based on physics, the rest was choice
or chance; things that did not work were dropped. An evolution basically. I
doubt there is a record of early music development as music must be 30,000+
years old.[... many neat ideas clipped for brevity...]