Tonic Triads
The first degree of the scale is also known as the tonic (or “doh”). A tonic triad is a chord built up from the 1st, 3rd and 5th degrees of the scale.
For example, here is the tonic triad in G minor:
It’s built on the tonic, G, with the 3rd degree of the scale, Bb, and the 5th, D.
The tonic triad is number one, because it’s built from the first degree of the scale. So, in Roman numerals we say it is “I” or “i”. We use capital letters for major triads, and lower-case letters for minor triads.
In lead sheets, you may see the chord symbol e.g. “Gm”, which stands for “G minor”.
Which Register?
It doesn’t matter which octave (or “register”) you write a triad in. Try to avoid using lots of ledger lines though! Here are two triads in C major, in different octaves:
Inversions of the Triad
When the lowest note of the triad is the same as the chord’s name, we say that the triad is in root position. The other two notes are each a 3rd higher than the note below. Here are some examples of tonic triads in root position:
If we change the order of the notes of the triad, so that the middle note becomes the lowest note, we say the triad is in first inversion. (“Inversion” means “turned upside down”). Here are the same chords as above, but in their first inversions. The other two notes in the triad are now a 3rd, and a 4th higher than the lowest note.
Important: When a chord is in an inversion, it is the lowest sounding note that we need to look at. You cannot tell an inversion by looking at the higher notes – only the lowest note (also called the “bass note”) counts.
When the top note from a root position triad is moved into the lowest position, the chord is in second inversion. Here are the same chords, but in second inversion. The intervals between the notes are now a 4th, and a 3rd.
Dominant Triads
The fifth degree of the scale is also known as the dominant (or “soh”).
A dominant triad is a chord built up from the 5th, 7th and 2nd degrees of the scale.
For example, in the key of C major, the 5th, 7th and 2nd degrees of the scale are G, B and D:
These three notes make a triad of G major. We can label this chord as V (with a capital V, which is the Roman numeral for 5), or simply as “G”, which means “G major”.
Remember that a triad of G major could also be called “chord I”. The Roman numeral name for a chord depends on the key the music is in. G major is chord I in the key of G major, but chord V in the key of C major:
In minor keys, we use the harmonic minor scale to build up the notes of the dominant triad.
Here is the scale of A harmonic minor as an example:
The 5th, 7th and 2nd degrees of the scale are the notes E, G# and B, so the dominant triad in the key of A minor is the triad of E major:
Because the 7th degree of the scale is raised up by a semitone in the harmonic minor scale, you will always need to add an accidental on to the middle note of a dominant triad, when it’s in a minor key.
Four-Part Chords
A triad is a kind of chord. Triads always have only three notes in them, but “chords” can have any number of notes. One of the most common ways of writing chords is in four parts. Usually the root (or lowest note) of the triad is doubled up an octave higher, and added to the basic triad.
The top three notes of the chord can be written in any order. The lowest note of the chord should be the root of the triad if the chord is in root position.
Here are some examples of a C major root position chord, written in different ways. Notice that the lowest note is C in every case, but the order of the other three notes can be different:
These four-part chords are written using a system called SATB, which stands for “soprano, alto, tenor and bass”. In this system, the chord is written on a grand staff (like a piano staff) with a treble and a bass clef stave joined together at the left with a bracket or brace.
On the treble clef we write the top two notes of the chord. The topmost note is called the “soprano” note, and the lower note is called the “alto” note. On the bass clef stave the topmost note is the “tenor” note, and the lowest note is the “bass” note. These four words can sometimes refer to the four main human singing voices, but they also refer to the general position of a note within a chord, even if the notes are played by instruments instead of voices.
When you write out a chord in SATB style, you need to pay attention to the stem direction of the notes. Soprano and tenor notes are always written with the stems pointing upwards, and alto and bass notes always have their stems pointing downwards.
When you write out a chord in four-parts, it’s also important to think about the spacing between the parts. If the bass and tenor parts are written close together, the chord can sound very “muddy” or indistinct. It is much better to write a wide space between the bass and tenor, and place the upper parts closer together. A good rule-of-thumb is keep the bass and tenor at least a 5th apart, and to keep the upper parts no more than one octave apart from the next note.
- is poor because the gap between the tenor and alto is more than one octave, and the gap between bass and tenor is less than a 5th.
- is good because the gap between bass and tenor is wide, and the gap between each pair of upper parts is narrow.
- is poor because the gap between the tenor and alto is more than an octave.
- is good because the gaps are spaced with the widest gap between the lowest two parts.
The Perfect Cadence
The tonic and dominant triads (or chords) work together in special ways in music. They are the two most important chords within music (in the Western world) because they are the chords which let us understand what key a piece of music is in, and help us to understand its structure.
Music is often organised into short “phrases” – these work a bit like sentences in language. A phrase is a musical idea with a clear start and end point. Phrases can be any length, but they are usually around 4 to 8 bars long.
Traditionally, the end of a phrase is always marked with something called a cadence. A cadence is a sequence of two particular chords – one followed by the other. The most common cadence is called the “perfect cadence”, and this is the only one you need to recognise for Trinity grade 3 music theory. You can think of a perfect cadence as similar to the “full stop” at the end of a sentence – it is a signal that the phrase has come to an end. A perfect cadence uses chord V (dominant), followed by chord I (tonic).
Here are some examples of perfect cadences.
Key: G major. Chord V (D major) is followed immediately by chord I (G major).
Notice how the 7th degree of the scale, F#, (also called the “leading note”) rises up a semitone to the tonic note G in the same part.
Key: E minor. Chord V (B major) is followed immediately by chord i (E minor). The 7th degree of the scale, D#, is followed by the tonic note E in the same part.
