C, octave
harmony:2 notes simultaneously X
Melody: collection of musical tones X
Octave: from a low note to its higher such that A to A, B to B, and so on
Scale: all notes between slim such that ABCDEFGA
Difference between octave and scale is the actual notes on a scale is between at least one octave. However, an octave does not contain a scale. Thus taking about 2 different A’s you say they’re an octave apart NOT a scale apart because octave is the ratio and the scale is a product of that ratio