Edits to docs

[composingcap]

Edited controlling sound and getting started sections in the docs. Cleaned up and reordered somethings for clarity.

I did quite a bit or rewording and organizing, so it may be worth looking at to make sure it still communicates what you want. I was thinking about teaching this to students as I did edits.

[giovannibedetti]

@all-contributors please add @composingcap for doc

[allcontributors[bot]]

@giovannibedetti

I've put up a pull request to add @composingcap! :tada: