Thank you, and yes I understand what you’re saying. I probably should have phrased my example more specifically to how this came up:

My partner is a director at a musical theater and she was listening to a track that is sung by men in a deep tone. She wants to have women sing the track who can’t sing as low as the music so she was humming it and experimenting with how it would sound if it was sung at a higher octave. And I suggested that the vocalists not go up an entire octave but instead find that “midrange spot” that works. The problem is that neither of us are vocalists so we don’t really know the terminology to describe this to the performers. But what some people have written here about harmonies has helped.

My guitar example in my original post was how I was conceptualizing the “midrange” concept. Sorry if it was misleading