answer: historical reachers use scrap books, speeches, journals, letters and diaries, photograges, audio recordings, video recordings, films, archives and manuscript material, published books, newspapers and magazine clippings published at the time.
Example: Speeches: mlk’s speech. Newspaper: news in the newspaper about Rosa parks. (Thats only two but you see where I’m going)
Not sure what graph you’re talking about but i know that when you play an instrument the pitches are different regarding the note and tone you play
<span>Balance
</span><span>Proportion
</span><span>Rhythm
</span><span>Emphasis
</span><span>Unity </span>
