Assuming a simple diatonic C scale, calculate the interval (integer) between two notes (provided as strings). By applying numbers to the notes of the scale (C,D,E,F,G,A,B,C = 1,2,3,4,5,6,7,8), intervals can be calculated. Because a unison is defined as one rather than zero, you add one to the numerical difference. The intervals are defined as:

C - C: perfect unison, 1

C - D: major second, 2

C - E: major third, 3

C - F: perfect fourth, 4

C - G: perfect fifth, 5

C - A: major sixth, 6

C - B: major seventh, 7

For example, if the input is {'C','G'} the output will be a perfect fifth: 5-1+1=5. For input {'E','A'} the output will be a perfect fourth: 6-3+1=4.

For intervals that wrap around the scale, add seven to the resulting negative number to obtain the correct interval. For example, for {'A','C'} the output will be a major third: 1-6+1=-4, -4+7=3.