Recently I started to take on my old hobby of music making and playing the keyboard, so i had also the need to brush up my knowledge on music theory These series of posts are mostly a summary for myself of information I found all over the internet. This first post concerns about basic intervals and chords
Intervals
An interval is basically the distance between 2 notes. These distances or intervals have names and are used as building blocks for chords. Some of the most common intervals are listed in the table below:
| Name | Description | Examples |
|---|---|---|
| Half step | Basic interval. White key -> Black key Black key -> White key (except between B and C and E and F, which are 2 white keys) | C-Db B-C |
| Whole step | 2 half steps White key -> white key (except between B and C and E and F) | D-E E-F# |
| Major 3rd | 2 whole steps | F-A C-E |
| Minor 3rd | 1 whole step 1 half step (or Major 3rd minus 1 half step | F-Ab C-Eb |
| Perfect 5th | 3 whole steps 1 half step (or Major 3rd plus Minor 3rd) | C-G Db-Ab |
| Diminshed 5th | 3 whole steps (or Perfect 5th minus 1 half step) | E-Bb D-Ab |
| Augmented 5th | 4 whole steps (or perfect 5th plus 1 half step) | F#-D C-Ab |
| Major 7th | 5 whole steps 1 half step (or octave minus 1 whole step) | C-B Ab-G |
| Minor 7th | 5 whole step (or Major 7th - 1 half step or Octave - 1 whole step) | C-Bb F-Eb |
| Diminished 7th | 4 whole steps 1 half step (or Minor 7th - 1 half step or Octave - 1 whole step and 1 half step) | C-A E-Db |
| Octave | 6 whole steps | C-C’ F#-F’ |
Chords
A chord consists of 3 or more notes separated by particular intervals.
Basic triads
A triad is a chord that consists of 3 notes. See the following table for the basic triads. The composition column indicates which intervals make up the chord from a particular root note. The notation column indicates how the chord is commonly written in non staff notation
| Type | Composition | Notation | Example |
|---|---|---|---|
| Major | Root -> Major 3th -> Perfect 5th | ROOTNOTE | C: C-E-G Ab: Ab->C->Eb |
| Minor | Root -> Minor 3rd -> Perfect 5th | ROOTNOTEm | Cm: C-Eb-G F#m: F#-A-Db |
| Diminished | Root -> Minor 3rd -> Dim 5th | ROOTNOTEdim | Cdim: C-Eb-F# Edim: E-G-Bb |
| Augmented | Root -> Major 3rd -> Aug 5th | ROOTNOTEaug | Caug: C-E-Ab Bbaug: Bb-D-F# |
7th chords
A 7th chord is a 4 note chord consisting of a basic triad plus an extra note which is a 7th interval from the root note. Not all combinations of triads and 7th intervals are ‘allowed’. See the table below. An X indicates that this combination is not ‘allowed’, all other entries are the chords that represent this combination.
| major 7th | minor 7th | diminished 7th | |
|---|---|---|---|
| major | M7 | 7 | X |
| minor | mM7 | m7 | X |
| diminished | X | Ø(m7b5) | O7 |
| augmented | augM7 | X | X |
The following table contains the composition of the 7th chords and the table is built up similar as the the one with the basic triads above.
| Type | Composition | Notation | Example |
|---|---|---|---|
| Major 7th | Root -> Major 3rd -> Perfect 5th - > Major 7th | ROOTNOTEM7 | CM7: C - E - G - B AbM7 Ab - C - Eb - A |
| Minor major 7th | Root -> Minor 3rd -> Perfect 5th -> Major 7th | ROOTNOTEmM7 | CmM7: C - Eb - G - B F#mM7: F# - A - Db - F |
| Augmented major 7th | Root -> Major 3rd -> Augmented 5th -> Major 7th | ROOTNOTEaugM7 | CaugM7: C - E - Ab - B |
| Major minor 7th (aka Dominant 7th) | Root -> Mqjor 3rd -> Perfect 5th -> Minor 7th | ROOTNOTE7 | C7: C - E - G - Bb Eb7: Eb - G - Bb - Db |
| Minor 7th | Root -> Minor 3rd -> Perfect 5th -> Minor 7th | ROOTNOTEm7 | Cm7: C - Eb - G - Bb Am7: A - C - E - G |
| Half diminished 7th | Root -> Min 3rd -> Diminished 5th -> Minor 7th | ROOTNOTEØ7 or ROOTNOTEm7b5 | CØ7: C - Eb - F# - Bb Em7b5: E - G - Bb - D |
| Full diminished 7th | Root -> Major 3rd -> Diminished 5th -> Diminished 7th | ROOTNOTEO7 | CO7: C - E - F# - A Bb: Bb - D - E - G |