Interval an interval is the number of alphabetical steps from the lower of the two notes to the upper, e.g. ‘A to E’, A-B-C-D-E. ‘E’ is the 5th alphabetical letter from ‘A’ therefore ‘A-E is a 5th. This is without exception. A ‘normal interval’ is one in which the upper letter is part of the major scale of the lower letter; ‘A-B-C#-D-E’, a major scale, therefore ‘A-E’ is a ‘normal’ interval, as well as ‘A-B’, ‘A-C#’, ‘A-D’.