It is well-known that there are infinite possible intervals, even if one confines one's view to a single octave. This includes the rational intervals of just intonation and the irrational intervals of EDOs, edonois, and other systems. However, it is helpful to consider interval regions (or interval categories), which there may be a finite number to consider.
Extended-diatonic interval names
- Main article: Extended-diatonic interval names
Many interval naming systems extend the diatonic interval names by adding new interval qualities to the usual set. While some systems preserve the fifth-based structure entirely, other systems define regions based on the proximity to the intervals associated with the diatonic intervals, which are then divided into finer subregions.
- In naming categories of intervals, or regions of the spectrum in which they are found, there may be many valid and desirable schemes reflecting the diversity of viewpoints and styles to be found in world musics. What I describe here is merely one possible solution, and one influenced by my own musicmaking experience and philosophy which seeks an equitable and inclusive balance between intervals at or near simple integer ratios, and those having a more complex or active nature.
Schulter proposes the following categories and gives a tentative range of cents values for intervals that fall within those categories. In Regions, she points out, "A main caution is that the borders are inevitably 'fuzzy,' so that one region shades into another and suggested values in cents are more illustrative than definitive."
|Interval Category||Associated Ranges of Cents Values (borders are "fuzzy")|
|Pure Unison (1:1)||0|
|Octave less diesis||1140-1170|
|Octave less comma||1170-1200|
|Pure Octave (2:1)||1200|
Pure unison (1:1) 0 cents Commas 0-30 cents (Section 11) Dieses 30-60 cents (Section 11) Minor seconds 60-125 cents (Section 5) small 60-80 cents middle 80-100 cents large 100-125 cents Neutral seconds 125-170 cents (Section 6) small 125-135 cents middle 135-160 cents large 160-170 cents Equable heptatonic (heartland range) 160-182 cents (Section 12) Major seconds (or tones) 180-240 cents (Section 4) small 180-200 cents middle 200-220 cents large 220-240 cents Interseptimal (Maj2-min3) 240-260 cents (Section 9) Minor thirds 260-330 cents (Section 2) small 260-280 cents middle 280-300 cents large 300-330 cents Neutral thirds 330-372 cents (Section 3) small 330-342 cents middle 342-360 cents large 360-372 cents Major thirds 372-440 cents (Section 2) small 372-400 cents middle 400-423 cents large 423-440 cents Interseptimal 440-468 cents (Section 9) (Maj3-4) Perfect fourths 468-528 cents (Section 7) small 468-491 cents middle 491-505 cents large 505-523 cents Superfourths 528-560 cents (Section 10) Tritonic region 560-640 cents (Section 8) small 560-577 cents middle 577-623 cents large 623-640 cents Subfifths 640-672 cents (Section 10) Perfect fifths 672-732 cents (Section 7) small 672-695 cents middle 695-709 cents large 709-732 cents Interseptimal 732-760 cents (Section 9) (5-min6) Minor sixths 760-828 cents (Section 2) small 760-777 cents middle 777-800 cents large 800-828 cents Neutral sixths 828-870 cents (Section 3) small 828-840 cents middle 840-858 cents large 858-870 cents Major sixths 870-940 cents (Section 2) small 870-900 cents middle 900-920 cents large 920-940 cents Interseptimal 940-960 cents (Section 9) (Maj6-min7) Minor sevenths 960-1025 cents (Section 4) small 960-987 cents middle 987-1000 cents large 1000-1025 cents Equable heptatonic 1018-1040 cents (Section 12) (heartland range) Neutral sevenths 1030-1075 cents (Section 6) small 1030-1043 cents middle 1043-1065 cents large 1065-1075 cents Major sevenths 1075-1140 cents (Section 5) small 1075-1100 cents middle 1100-1120 cents large 1120-1140 cents Octave less diesis 1140-1170 cents (Section 11) Octave less comma 1170-1200 cents (Section 11) Pure octave (2:1) 1200 cents