I have just started learning music theory and I have learnt intervals and I have gotten up to learning the cantus firmus.
I have two questions: On the piano keys, when I count interval steps, am I to include both the black and white keys or only the white keys. The instructions says for cantus firmus, I am only to use a diatonic scale, but for counting intervals am I still to count the black keys also? So even on a diatonic scale F to E is 11 half steps which is a major seventh.
The cantus firmus below is an example composed by Heinrich Schenker and has the following notes and the intervals from note to next note counting both white and black keys on the piano:
c1 d f e f g a g e d c
2,3,11,1,2,2,10,9,10,10 (intervals of above notes)
Why is Schenker using both major seventh (11 half steps) and minor seventh (10 half steps)? I was told at the beginning of the lesson to avoid dissonant intervals and I believe the seventh is considered dissonant.
Here are the links to the example I was using:
I am still a beginner to music theory, but I hope I made myself clear. Thanks.