If you aren't experienced in music theory, do not be surprised if you encounter some confusion along the way.
Western music theory relies on principles which have been redefined and reinterpreted. Yet, at its core it's quite straightforward - some would say it's just perfect fifths.
The concept of diatonic scales relies on the major scale and what can be derived from it. A novice might be surprised still, when hearing that there are minor scales built from seven notes, which are not considered diatonic.
We'll take a look at why a major scale is a diatonic scale. Why the natural minor scale has the same notes as its parallel major counterpart, yet sounds very differently. We'll also see what are diatonic chords.
We'll reference the piano keyboard, as the diatonic system is most easily explained through it.
Historical references will be brief; history is for another time. We're here to learn why C D E F G A B C is a diatonic scale and not a chromatic scale... Let's not invent hot water along the way...
To keep things simple, we'll just note a few useful terms here:
- Intervals are the distances between two notes.
- A key signature is defined by the starting note of a major or minor scale.
- A half step is the shortest possible interval between two notes.
- Naturally, a whole step consists of two half steps.
So, What is a Diatonic Scale?
A diatonic scale is typically defined by a fixed series of whole steps (aka whole tones ) and half steps (aka half tones or semitones ).
To be considered a diatonic scale, the scale has to contain exactly five whole steps and two half steps, arranged in a strictly defined way. As noted, the major scale is the most well known example of a diatonic scale.
You probably already know that the notes C D E F G A B C constitute the C major scale. C is the starting note, as well as the ending one, so eight notes in total, seven unique ones.
If we take a look at a piano keyboard, we'll notice that these are all white keys. However, between some neighboring white keys there are black keys, and between other ones there aren't.
There are no black keys between E and F, as well as between B and C. These constitute the two half steps. In addition, we can confirm that the major scale has five whole steps.
*For the slightly more experienced reader, we'll just note in passing here that the harmonic minor scale is not a diatonic scale. The melodic minor isn't either. This is because their two half steps are positioned too close to one another. They need to be at least two whole steps apart.
How Many Diatonic Scales Exist?
Seven. Take the diatonic C major scale, but play the sequence from A to A (i.e. A B C D E F G A). You're in a minor key now and the scale is A (natural) minor scale. From the perspective of C, it is also a relative minor scale.
Here we'll just add that this can be done from any other starting position, any scale degree of the major scales. That's why we said seven. Seven different sounding diatonic scales.
On each scale degree in this context, a scale can be built, consisting of seven tones. Hence, from a single major scale, seven diatonic scales are derived.
The theory of western music traditionally studies the major and minor in depth. All the seven scales are well known of course, though some of them are typically less intensely studied.
Interestingly, all seven were known as "church modes" historically and were equally popular during the middle ages. All were popularized again with the advent of jazz harmony and theory.
So There Are Seven Modes Then!
Yes, there are seven diatonic modes. A diatonic scale features only seven notes (seven unique notes) always, hence a diatonic mode does also.
Returning to our C major example, the major scale is also known as Ionian mode .
The same notes but from D to D constitute the Dorian mode. Next is the Phrygian mode (from E to E), followed by the Lydian mode (from F to F). G to G defines the Mixolydian mode, whereas A to A is the natural minor scale or Aeolian mode. B to B constitutes the Locrian mode.
From the major's sixth degree we derive the relative minor i.e. the Aeolian mode. This the minor diatonic scale.
*One might think that seven notes constituting seven modes somehow means that the seventh degrees of the modes are always relevant. But this isn't the case, as it depends on the context. They are, at times, the leading tone, and other times just a color tone, and sometimes simply irrelevant.
But What Constitutes a Musical Scale In General?
Interestingly, some authors refer to musical scales simply as sequences of notes...
Alright, but what isn't a scale then?
Yeah, the above isn't correct. Two notes constitute a sequence, but certainly not a scale!
Furthermore, a given interval sequence can be outlining a chord , as traditionally defined, rather than "a scale". The notes of a major triad, a minor triad and by extension all major and minor chords are a good example.
Taking this even further, extending by repetition, such as C E G C E G C does not constitute a note scale also.
Likewise, the sequence A C E A C E A is contained in the natural minor scale, but alone does not constitute a scale.
Is C ♯ D A B C a Scale?
A sequence of no less than 5 notes in ascending (or descending) order constitute a scale, according to others.
Natural scales and scale degrees, are defined by particular sequences of whole and half steps. However, a sequence of notes featuring an interval wider than two whole tones isn't really considered a "scale".
Most will agree that neighboring scale degrees can not be more than one and a half step apart. A scale then consists of half and whole steps, whereby a step and a half is also allowed, provided another one does not appear immediately thereafter.
What Other Types of Scales Are There?
The rest of the field is populated by non diatonic scales. The most well known among these is the chromatic scale.
Of the non diatonic variants, the most "narrow" is the chromatic scale, whereas the most "wide" is the pentatonic (minor or major, with the former being far more popular).
Chromatic simply means that no note is skipped, i.e. all are used and thus the scale constitutes of 13 notes. The 13th note is the same as the starting one.
The thing is, any scale which features notes that do not belong to a major of a natural minor scale as such is considered a non diatonic scale. And these can't be listed; virtually anything goes.
Do C C ♯ and D Constitute a chord?
In contemporary theory: sure! This is because a chord is no longer needed to be defined by a sequence of thirds (or their inversions).
The context of a diatonic scale and diatonic chords has not been abandoned, but rather extended. Major keys are still major keys; the diatonic scale is defined the same, as we've already seen.
The thing is, half steps have sort of emancipated, along with whole steps. A scale degree will depend on how many musical notes are used, and not on their "diatonicity" (now that's a new word!)
Thus, the context of a root note in the chordal sense is less relevant than earlier. "The white notes" on the piano aren't less relevant of course. It's just that other approaches have risen to prominence also.
Sounds Like a Sequence of Notes Can Both denote a Scale And a Chord...
Take the western music scales and play all the notes simultaneously. You got yourself a chord! At least three notes sounding simultaneously constitute a chord.
In contemporary context, be it a whole tone or any of the diatonic scales - anything goes. Play the notes simultaneously and you're playing a chord!
What Are The Most Popular Scales (And Why This is the Case)?
Well, the basics are constituted of diatonic and chromatic scales. The major scale (the Ionian mode) still stands at the pedestal's top, of course.
Of the modes which can define a minor triad, the Dorian mode rose in popularity tremendously, during the 20th century. This is due to its use in both Jazz and Rock music.
It depends on the genre and personal tastes really. This text's author is fond of the church modes simply because they (or their variants) are present in the folk music of virtually the entire world.
A lover of western music therefore, does not have to prefer diatonic chords or a diatonic scale. Or seven notes over any other number of notes. So long as a different note is played often enough, there'll always be space for creativity and artistry!