Each chord type is based upon a unique formula which can be related back to the major scale that has the same letter name as the chord, e.g. C chords are based upon a formula that can be measured against the C major scale. Here is the C major scale written in standard music notation and tab (tablature). If you play these notes you would get the familiar Do Re Mi Fa So La Ti Do sound.
The letter name of each note is written below the note on the staff (3). Below the letter name is the degree number of the note in the scale. These thirteen note degrees are all that is needed to create all chord types. Each chord type will have its own unique formula.
The formula for a major chord is 1 3 5 which means that each major chord consists of the first, third and fifth notes of the related major scale, e.g. the C major chord consists of the 1st, 3rd and 5th notes of the C major scale (C E G). These notes can be in any order and can be duplicated but there must be at least one of each of those notes, e.g. in the adjacent C major chord shape there are two C notes, three E notes and one G note. The G major chord consists of the 1st, 3rd and 5th notes of the G major scale (G B D).
The formula for a minor chord is 1 b3 5 which means that each minor chord consists of the first, flattened third and fifth notes of the major scale.
e.g. the C minor (Cm) chord consists of the 1st, 3rd and 5th notes of the C major scale (C Eb G). So even though it is a minor chord, the chord formula still relates back to the major scale.
A full understanding of chord construction is essential as your playing ability advances, as it is particularly useful when improvising, substituting or writing an accompaniment for a song or piece of music.
The following chart lists all the chord types used in this book, along with the formula for the note degrees from the major scale, plus an example of each chord type in the key of C. Study the chart well, so that you can see the relationship of each chord type to the C major scale on the previous page.