How come modern modes are based on the same set of intervals?

Question

I couldn't find any answer regarding this specifically, so I assume there's some basic concept behind this that I missed.

So, as far as I know:

Modern modes are based on the same set of intervals, as seen in this picture.

To play in a modern mode you would just have to start from a different degree of that set of intervals, and you would have a mode.

This evokes my curiosity: why is this pattern so crucial? After all, a scale can be composed of any allegedly random set of intervals. So how did this specific pattern came to be? And what explains the adherence to it, compared to going full on crazy and using interval patterns that are remotely different from this pattern? (In western music, at least.)

Thank you for your time.

Answer 1

why is this pattern so crucial?

It isn't, really - it just happens to subjectively work pretty well, with most of its starting points (apart from, arguably, the Locrian) yielding modes that have interesting harmonic and melodic possibilities.

After all, a scale can be composed of any allegedly random set of intervals.

Well, it depends what you're trying to achieve. If you want to allow consonant harmony, it makes sense to have some notes that are consonant with your root note, and with other notes in the scale; If you look at the notes in the diatonic scale, it allows 6 fifths, 6 fourths and 3 major thirds, for a start, in a scale with only seven notes - which seems quite a good yield to me. (The fact that there are 6 fifths relates to Michael Curtis' point that the diatonic tones can all be rearranged as ascending perfect fifths.)

And what explains the adherence to it?

I don't think there really is an adherence to it, if you look at a wide body of music. Minor key harmony? Usually goes outside of the diatonic scale. Modern major key harmony, for that matter, too. Whenever anyone 'modulates'? They probably go outside of the diatonic scale. 'Borrowed chords', likewise. Blues scale? Not diatonic.

Of course a lot of cases of these might be said to be almost diatonic, or represent a motion between one diatonic scale and another, or somesuch. Which is fine if it helps you as a way of communicating or doing your own analysis.

In case it sounds like I'm trying to denigrate or disenfranchise the diatonic scale, I am not. I like it!

Answer 2

If you want to focus on scales made from steps in the chromatic scale, 12TET tuning, then there are dozens, at least 72 that I can think of (actually twice this if my memory is correct). In the Carnatic style of music from India one builds scales using only notes from the 12TET chromatic scale with a few restrictions. The larger set of Carnatic scales can have different ascending and descending patterns and do not have to have 7 tones. However there is a set of modern Carnatic Ragas called Melakarta Ragas that all have 7 tones. The set of 72 has a restriction of having a P5 (the dominant) present. Other than that one has every possible unique combination of 2nds, 3rds, 4ths, 6ths, and 7ths. And by every they allow major, minor and diminished intervals, as long as they do not coincide with the next note. For example if a Raga has M2 it can have M3 and m3 but not d3. However if the Raga has m2 then it can have a d3 (double flatted 3rd). This allows for chromatic bits separated by large intervals. From this set a whole new set can be generated by either augmenting or diminishing the 5th, for those Ragas that do not have a m6, or a4, respectively. Between the modern Ragas and traditional Carnatic scales there must be well over 100.

So as part of your question the "modes" you have listed are simply those that Europeans have converged on.

A second part of your question seems to be more historical and cultural than technical. The seven modes you have listed align the way they do primarily thanks to the 12TET tuning. Keep in mind that over a few thousand years these scales became more widely used in Western European Cultures than others, and there were others. Also, as music became standardized there was a desire to transcribe (or simply write) older folk tunes in new standard music notation. This introduced changes to original tunes to get them to fit as best as possible to the standard Major scale that was evolving. Sort of like a nearest neighbor interpolation applied to the notes. If you do a search you may find some information on ancient modes that eventually became Dorian, Phrygian, etc. The ancient versions did not sound exactly as the modern equivalent. Add to this the fact that many eastern musical styles use 1/4 tones. There is a Turkish instrument called the Saz which is guitar like and has quarter tone frets. Similar things exist in Persian music. Persian music has a great influence on classical Spanish music but the Guitar has evolved to 12TET tuning. So melodic phrases are modified to fit as closely as possible to the diatonic scale. A combination of many factors probably led to the diagram you posted in your original question. In addition to some I've mentioned I'd include the evolution of large orchestras and the complex harmony probably forced the need for simpler standard scales as there is less improvisation in Western classical music and choir music than in folk music.

At the end of the day these are the memes that survived. They developed while others were lost by force. By the influence of composers and performers who preferred these scales.

Reference: Classical Music of India by Subramaniam and Subramanium

Answer 3

In order to narrow down the possibilities, let's focus on heptatonic scales with only whole and half tone steps. As a second restriction, let's agree that we don't want two consecutive half steps in our scales. These restrictions might seem arbitrary, but they are quite reasonable from a melodic and harmonic standpoint (for western ears, at least).

Apart from the modes in your question, it might surprise you that, given above restrictions, there is only one more 7-note scale (and its modes) that has a different pattern of whole and half steps: the melodic minor scale. In that scale the two half steps are separated by only one whole step. The modes of melodic minor are used a lot in jazz, so we actually do not exclusively adhere to the church modes.

Note that if we allow two consecutive half steps then there's again only one more scale (and its modes): the Neapolitan major scale. So there are only three systems (i.e., 3x7 = 21 scales) of heptatonic scales with only whole tone and half tone steps: the major scale and its modes, the melodic minor scale and its modes, and the Neapolitan major scale and its modes. All other scales either have at least one interval that is neither a half step nor a whole step, or they have more or less than seven notes (like the pentatonic minor and major scales, the whole tone scale, the diminished scales, bebop scales, etc.).

If you really want to go crazy, you should consider leaving the heptatonic scale system in 12-TET and look for new sounds in different temperaments.

Answer 4

One of the meanings of "mode" is simply the "rotation" of a scale. Playing the second mode of the major scale means to play the scale tones, but starting on RE, the second degree. In that sense "mode" means to not change the set of intervals of the scale but simply to rotate them.

The second point is the modes you listed are all diatonic modes. That is a crucial pattern in much music, because the diatonic tones are the foundation of the major/minor system. Why? One explanation is the diatonic tones can all be rearranged as ascending perfect fifths and that interval is acoustically significant.

The are many other modes. The modes of harmonic minor and melodic minor are pretty common in several different musical styles.

Answer 5

You're starting out from a false premise. Yes, there are 7 scales derived from the major scale. Label them the 'modern modes' if you like. That doesn't give them any special status, or even imply they're used more often than other 8-note scales. Historically, Harmonic Minor has probably been used more than any of the 'modern modes' except Ionian (major).

Answer 6

You mention western music right at the end -- do you mean your question to be confined to just western scales? If so, then one factor which limits the choice severely is the prevalence of a temperament with just 12 pitches per octave. It leaves a limited number of options for each degree of the scale.

The 7th degree can be major or minor

The 6th degree can be major or minor

The 5th degree must practically be a perfect fifth above the tonic (if it isn't, the tonic triad sounds dissonant, and that is the one triad you want to sound consonant)

The 4th degree can be perfect or augmented

The 3rd degree can be major or minor

The 2nd degree can be major or minor

Even so, this allows some scales which are not in your list, e.g. the double harmonic major, Hungarian major, double harmonic minor (Hungarian minor) and Romanian Minor (Ukrainian Dorian) scales.