Reading assignment: PpP 7.1-7.3
Why does a trumpet playing a 440 Hz note sound qualitatively different than when
a violin plays the same note? Both are producing 440 Hz waves, aren't they?
Both are producing a waves with a period of 1/440Hz, but the *shapes* of the waves are different. This means that although both have a fundamental frequency of 440 Hz, the amplitudes of the higher harmonics could be very different. It's those higher harmonics that produces the tone quality (as opposed to pitch, which is set by the fundamental).
What is a chapter on musical scales doing in a physics textbook? What's the
connection to physics?
The main connection to me seems to be harmonics. The Pythogorean scale and "just intonation scale" are all about integer ratios of a fundamental frequency. That's just the same as the harmonics of a string/open pipe that we learned about in a previous chapter. Beats are also a connection... the main issue with the "equal temperament" scale is that notes are slightly out of tune with the desired integer ratios. That causes unwanted beats.