This post is one of a 2-part series of free basic music theory lessons on my blog, musictheoryde-mystified.com. You can see the complete list here. Please feel welcome to make a comment or ask a question.
The chromatic scale
The chromatic scale is made up of every one of the 12 musical note pitches, each 1 semitone apart from the next. It is the parent of all modes (…except in cultures with more than 12 note pitches per octave…).
Apart from some largely academic genres such as serial music, chromatic scales are mainly used as musical effects, such as the rapid chromatic passages used to build tension and drama in film music.
As a key, the chromatic scale has no inherent tonality: there’s no way to tell the root note from any other note. That’s not to say that you can’t nominate a root note, just that it requires a lot of effort to make that root note felt in a piece.
I don’t mean that it has no musical character, either. It does, but it’s a very nebulous one…
Modes
A mode is the pattern of intervals that determines which of the 12 different note pitches within an octave are used to produce a scale/key. Apart from the chromatic scale and the “whole tone scale” (6 notes within an octave, with 2 semitones between each note and the next), modes have an irregular pattern to their interval structure. As long as the root note is highlighted from time to time this irregularity allows a mode’s unique character to permeate the character of the music.
Diatonic Modes
The traditional Western modes, such as ionian (major) and aeolian (minor), are made up of one- and two-semitone intervals. Such modes are called diatonic modes; modes whose scales only have two different size intervals between their notes.
Just to be confusing, they’re also called heptatonic modes, meaning that they have 7 different notes within an octave. The traditional modes are all made up of 7 different notes, where the eighth note is the octave of the first.
A mode doesn’t innately have these limits. For example, the harmonic minor (discussed later in this course) still has 7 notes but one of its intervals is 3 semitones, that between the 6th and 7th notes of the scale. Other modes have a different number of notes per octave, such as pentatonic (5-note) modes and the blues mode. Some modes even use one or more different notes ascending and descending. The melodic minor works like that, as do some Indian modes.
However, the most common modes in most Western genres are the traditional Western modes which evolved out of the Renaissance era.
Although often associated with period music and traditional folk music, some modes, such as the myxolydian mode, are commonly used in a variety of other genres. Jazz goes even further by using relative modes as an approach to improvising around extended chords.
What Are The Traditional Modes?
Let’s have a look at the natural notes for two octaves. Each note can be the root note of a diatonic mode (yeah, I wouldn’t worry about the “heptatonic” bit, it seldom crops up in conversation…).
Look at the notes for an octave, starting on each note in turn. Each root note produces a different pattern: a different mode.
We can compare their interval structure by lining them up underneath each other.
Each different mode has a unique quality that greatly influences the overall character of music played in that mode.
- You can hear this, even by just playing a scale.
- You can also teach yourself a new mode just by reading and playing the notes of the scale.
- If you play by ear, follow its pattern of intervals on your instrument by counting semitones.
Below is a scale of each mode starting on A, so we can compare their character..
A aeolian (natural minor)
A locrian
A ionian (major)
A dorian
A phrygian
A lydian
A myxolydian
The character of each mode is easy to identify in a melody. Have a listen to this short, simple melody played in each of the modes…
Simple melody in A aeolian (natural minor)
Simple melody in A locrian
Simple melody in A ionian (major)
Simple melody in A dorian
Simple melody in A phrygian
Simple melody in A lydian
Simple melody in A myxolydian
Modes And Key Signatures
The way in which key signatures are used for modes other than major or minor depends on genre and school. There are two approaches: like major/like minor or the mode’s actual key signature.
Like Major or Like Minor
Classical musicians are brought up on a strict diet of major and minor (as well as two variations of the minor, melodic minor and harmonic minor). A classically trained player is only going to look for two possible root notes when interpreting a key signature. Music in a less familiar mode would be hard to interpret on first reading; the root note would seem to conflict with the key signature.
The most important notes of a scale are the root note and the note 7 semitones above the root note, called a perfect 5th (don’t worry about the interval name, we’ll look at interval names soon). The perfect 5th helps stabilise the root note.
There is one other important note, the 3rd note. One reason the 3rd is important is because it’s the most significant difference between major and minor. In the major mode the 3rd note is 4 semitones above the root note and in the minor it’s 3 semitones above the root note.
We can categorise the other modes as being “like major” or “like minor”, based on the 3rd note.
Below is a list of the modes staring on A, grouped in “like major” or “like minor”. The note in the other modes that differs from the major or minor is highlighted.
Note that the locrian mode is not in either list! The locrian mode wasn’t used in Western music, or even named, until relatively recently because it lacks the essential ingredient of a perfect 5th. By not having a note 7 semitones above the root note, music written in this mode is elusive. We naturally listen for a root note but we either can’t find it or we’re misled by other possible root notes that do have a perfect 5th but don’t hang around long enough to feel convincing.
It’s VERY hard to make the root note stick in the locrian mode. Modes without a perfect 5th need almost constant reinforcement of the root note in order to be musically stable. One way to achieve this is by having a drone accompaniment, where the root note persists throughout the piece.
Accidentals
- For modes which are like major, we use the key signature of the parallel major mode; the major mode on the same root note.
- For modes which are like minor, we use the key signature of the parallel minor mode; the minor mode with the same root note.
This requires the use of an accidental. Anyone who’s seen music written in the melodic or harmonic minor will be used to accidentals used in this way.
For example, let’s look at one of the more common modes, the myxolydian mode.
- Using only naturals (key signature of 0 sharps/flats), the myxolydian mode starts on G. The actual key signature of G myxolydian is 0 sharps/flats.
- The myxolydian mode is like major, so for a ”like major/like minor” key signature we would use the key signature of the major mode on G, G major, which is 1 sharp (F#).
- To preserve the intervals of the myxolydian mode we need to flatten the 7th note, the note which differs from the major of the same root note, F# (remember, in the cycle of 5ths, the latest sharp is the 7th note of the scale…).
- When we flatten F# we get F natural, so for the first F in every bar that has one, we write a natural sign as an accidental.
*NOTE: An accidental is only written for the first instance of a given note in each bar.
Try These…
Like Major, Like Minor
Write the scale of the following modes for 1 octave ascending using the key signature of its parallel major or minor (the major or minor key with the same root note) and an accidental where required. Base your decision on whether the 3rd note belongs to the parallel major or parallel minor.
NOTE: Accidentals aren’t written as part of the key signature. They must be written beside the first instance of that note in every bar where that note occurs.
- A dorian
- D lydian
- C ionian (trick question… just seeing if you were paying attention)
- C myxolydian
- B phrygian
- F# dorian
- Bb myxolydian
Answers at the end of this post.
Actual Key Signature
Players of early music and traditional folk music, as well as a number of other genres, are quite familiar with the traditional modes. Typically, in such genres the actual key signature is used.
In the above example, G myxolydian is written in the key signature of 0 sharps/flats, rather than in the key of G major with F natural as an accidental. It’s cleaner and simpler to read (as long as you interpret the key signature correctly when reading).
When first reading a piece knowing only it’s key signature, you might wonder how to determine the root note of the piece, with so many modes to choose from. The approach is the same as when you’re just looking for major or minor. Look for an obvious note near the start and end of the piece.
For more on how to tell which note of a piece is the root note, please have a look at How Can We Tell Which Key We’re In?
Pentatonic modes
Pentatonic modes (5 notes per octave) are quite popular in various genres. Having only 5 notes, we can think of them as a subset of the traditional heptatonic modes that we’ve already looked at.
The most well known of these is the minor pentatonic mode, notes 1, 3, 4, 5 and 7 of the natural minor/aeolian mode. In this instance, we would use the key signature of the “parent” minor key. Other Western pentatonic modes are also subsets of parent modes, so we would use the key signature of the “like major” or “like minor” mode of which it is a subset.
Here are the two most common Western pentatonic modes.
Not all pentatonic modes are related to a parent Western mode. Any combination of 5 notes within an octave can be used as a pentatonic mode.
The Blues Scale
The most common mode in blues is a hexatonic (6-note) mode based on the minor pentatonic, with an extra note added between the 4th and 5th notes. From a notation viewpoint, there is no room in the naming system for the extra note to have its own letter: instead, it is considered an alternative to the 4th or 5th note and should be named according to its use. Either option requires an accidental.
Other Modes
Most musical cultures around the world have a concept of modes, a system of choosing a set of notes within an octave based on a root note and the intervals between its scale notes. Some use different intonation (tuning) systems: such modes can sound unfamiliar to the Western ear. Many are based on the same intonation as Western music, 12-Tone Equal Temperament, yet may have different numbers of notes per octave or notes that differ when ascending or descending. If you wish to experiment, you can create your own mode for a new composition or improvisation.
Freedom From Modes
The Western modes were originally used as a rigid framework for determining which notes were used in a composition. Over time, as music developed towards the journey through various visiting keys that it largely is today, the use of accidentals became more and more common, to accommodate these temporary keys.
Accidentals are also used for embellishment (ornamentation). Ornaments are treated as effects: an ornament may well use notes outside the key, requiring an accidental. This may extend to chromatic passages involving several accidentals.
The contemporary view is that a key is based on the overall use of the notes of a major or minor key, with the option of sharpening/flattening notes or incorporating other notes as desired.
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NEXT LESSON: 16. Intervals 1: Major, Minor And Perfect Intervals
PART 1 CONTENTS: Basic Music Theory Course Contents
Answers to Try These…
