Pitch-class prevalence in plainchant, scale-degree consonance, and the origin of the rising leading tone
Richard Parncutt
The most common tones in Medieval plainchant were G and D; the least common, B. I propose that individual scale degrees differed perceived consonance depending on number of audible partials (harmonics) corresponding to degrees. first ten harmonics correspond (G, D, B, F, A), but not those B (B, F#, D#, A, C#). More consonant sung more often became stable (reference pitches). Tones C F (fa) than E (mi). melodic semitone psychologically associated with a difference stability.
Journal of New Music Research