The mazurka movement and the augmentedfourth degree of the scale (Nos.
2
Tritone, augmentedfourth, known as "the devil in musick" from early medieval times.
3
The melodic progression, not always immediate, of an augmentedfourth and major seventh occurs frequently, and that of an augmented second occasionally.
4
The oriental interval of the augmentedfourth, which I scent in the "Mondlied," would be written, I think, more simply thus:-