Suggested Learning Resources
To calculate the ordered-pitch-class-interval between two notes...
- Convert the letter names of the pitches to integer notation
- If the two notes appear in the order of X, Y do the following calculation Y-X
(mod12)
- The result will always be an interval number between 0 and 11
- Example B4 to A3 become the numbers 11 and 9. 9-11 = 10 (mod12)
- You can also check this by counting how many steps it takes to move around the
clockface, clockwise, from starting pitch 11 to ending pitch 9 (10 half-steps)
To calculate the unordered-pitch-class-interval between two notes...
- Convert the letter names of the pitches to integer notation
- Find the shortest possible number of half-steps between the two pitches regardless
of order or direction
- One method is to calculate X-Y and Y-X (mod12) and use the smaller of the resulting
values
- The result will always be an interval number between 0 and 6
- Example B4 to A3 become the number 11 and 9 ... 11-9 = 2 and 9-11 = 10 (mod12)
... Thus the unordered-pitch-class-interval is 2
https://youtu.be/N9RRuX-lE0g?t=2m37s
Objective 49.2: Calculate ordered-pitch-class-intervals and unordered-pitch-class-intervals