 In connection with the application of regular numbers to music theory, it is of interest to find pairs of regular numbers that differ by one.There are exactly ten such pairs ("x", "x"+1) and each such pair defines a superparticular ratio ("x" + 1)/"x" that is meaningful as a musical interval.These intervals are 2/1 (the octave), 3/2 (the perfect fifth), 4/3 (the perfect fourth), 5/4 (the just major third), 6/5 (the just minor third), 9/8 (the just major tone), 10/9 (the just minor tone), 16/15 (the just diatonic semitone), 25/24 (the just chromatic semitone), and 81/80 (the syntonic comma).