Why harmonize non-diatonic notes with major 3rds above, in a

1. Why do some notes harmonize?
2. Can you harmonize is 3rds?

Why do some notes harmonize?

All over the world humans have independently chosen to put the same intervals between notes in their music. The feeling of harmony we get when we hear the notes C and G together and the feeling of disharmony we get when we hear C and G flat together turns out to be part of the universal human experience.

Can you harmonize is 3rds?

Harmonization Using Thirds. The traditional practice for harmonization in third intervals is that you harmonize a given note using another note that is a third below it. However in the case of the first tone of the scale we'll be going down a fourth instead.