The harmonic language of Cours d'Harmonie de Nadia Boulanger is entirely drawn from one of the few surviving classroom notes of Nadia Boulanger’s teachings (and therefore is entirely tonal). Because the harmony, due to its purity, feels rather flat, the remaining characteristics——especially timbre——help sustain the listener’s engagement. At times, tonal clarity is deliberately obscured, introducing moments of ambiguity that counterbalance the potential disconnection or boredom the harmonic material may produce.
Bibliography:
Bonet, N. (2006). Les principes fondamentaux de l'harmonie. Dinsic Publications.