Music Theory: Chords and Scales

Requisite Knowledge Level for Understanding (* being beginner, ***** being expert): *

So now that you know the basics to reading music, let's get into the basics behind the music itself.  The most basic foundation of music is either the Chord or the Scale, depending upon to whom it is you are speaking, but essentially that's like arguing whether the Hydrogen or the Oxygen is the foundation of the water molecule.  It really doesn't matter because the the water molecule functions as a whole using both interchangeably.

The word Chord literally derives from the Middle English word "accord" meaning "in agreement", as in, "these notes agree with each other".  This essentially means that they "sound good" together.  While, technically speaking, you could say that any two notes sounded simultaneously form a chord, most people will refer to a chord as having at least three notes.  A chord can have more notes, though most common chords will be comprised of three or four distinct notes.

A Scale, on the other hand, is a collection of notes which span the complete octave.  There can be anywhere from a few notes (e.g. five) to all twelve, though most common scales have seven distinct notes.  Generally these are arranged by pitch in lowest to highest, with the lowest note being the base note, or Tonic.  (This was covered in the previous post but is included here as a reminder.)

Chords are nice to use because they provide depth to the melody.  Hearing someone sing is nice.  Hearing someone sing while there's a piano playing behind them can help make the music to be more enjoyable and engaging (besides helping the singer not to feel so stressed about being the only musician actively performing).  Some notes sound good with other notes, some do not.  Chords help us to define which notes do and do not sound "good" with each other as well as what times to use what collection of notes.  These notes that might not sound "good" with each other as sustained notes are far from useless, as they can be used to propel the melody forward, leading it upwards or pushing it back down as the closeness of the notes in these chords can urge the music in either direction.

The scale is used to form chords; these are called Diatonic, literally and simply meaning, from the scale.  The melody is written primarily with notes from a scale, and thus the chords backing up the melody are taken from the same scale, making it all sound pretty.  As an example, let us again use the C Major Scale (C D E F G A B C).  The standard chord is formed by stacking three notes on top of each other in thirds, or every other note.  For example, the root chord for the C Major Scale is formed then by C, E and G.  You can then form chords that have a base note as each of these seven distinct notes in the scale, e.g. the chord based on the sixth note, the A, would be formed then by A, C and E.  These are then traditionally labelled by Roman numerals, one through seven, as indicated below, specifically this time being given again as an example in C Major.

                       C          D         E         F         G         A         B         C
                       I           ii         iii        IV        V         vi        vii^o       I

You will notice that the chords for C, F and G are listed with capital Roman numerals, while D, E and A have lowercase ones and B has lowercase numerals plus a superscript 'o'.  This denotes the quality of the chord.  The diatonic chords in the C Major scale built upon the notes C, F and G are Major Triads, which is defined by the distance between the first two notes being a major third (four half steps), and the distance between the second two notes as a minor third (three half steps).  The chords built on the notes D, E and A are Minor Triads, which reverses the major definition, with the distance between the first two notes being a minor third and the distance between the next two notes as a major third.  Lastly, we have the chord built upon the note B, which is a Diminished Triad, which is defined as having the distance between the first two notes as a minor third as well as the distance between the second two notes as a minor third.  These three types of triads, together with the Augmented Triad (formed by having the distance between the first two notes as a major third while the distance between the next two notes is also a major third), form the basis for most every chord (Triad and Chord can essentially be used interchangeably, with the word Triad simply more specifically indicating a chord comprised of exactly three notes, but you will hear both).

The most important chords in any key (i.e. scale), are the I or Tonic and the V or Dominant chords.  When a classical piece reaches the I chord at end of a phrase, you can tell.  It sounds like the "home" chord.  In a generic chord progression, the changing chords help to push the music further on and forward to which then the I/tonic chord brings what feels like a moment of peace after the push and pull of chords during the phrase.  The chord that you will see leading up to this phrase-ending tonic chord is nearly always the V/dominant chord, and quite often the chord before that one will be the ii chord.  This phrase ending pattern of V-I is generally referred to as a Perfect Cadence.


So when someone refers to something as a Key Change, what the music has accomplished at that point is the tonal shifting of the melody from that scale and set of chords (e.g. C Major) to another one (e.g. G Major), meaning that both the melody and the chords from that point on will generally now be taken from the G Major Scale.  This is almost always accomplished by using accidentals to stress the chords in a melody enough to push the chords to the point where the cadence then commences in the new key.  You can usually tell when a key change occurs because it will sound like the "home" note has gone up or down in pitch and it feels like something has shifted in the music.  Chords will be covered in further depth in later posts to be sure as this is just the very basis of how they interact.