Pentatonic
This video shows a green chord (c,e) – technically two tones are called an interval and 3 or more a chord, so perhaps ‘harmony’ is a more appropriate word for this – and the tones that sound well on it (shades of green) g,d,a.
These five tones together – 1,2,3,5,6 of the major scale – are known as the pentatonic system.
The major pentatonic scale (penta means five) = 1,2,3,5,6 or c,d,e,g,a in the major key of C.
The minor pentatonic scale (same tones, different order) 6,1,2,3,5 results in A minor pentatonic.
Translated* back to C; C minor pentatonic is c,e flat,f,g,b flat or in numbers 1,b3,4,5,b7. *this translation from one key to another is the act of ‘transposing’ music.
The pentatonic system is the base of many hit songs!
Blues
In blues, the minor pentatonic scale is used on both minor and major chords, and the minor pentatonic scale of the tonic (1) of the key can even be used on all chords of a blues. For example C minor pentatonic (c,e flat,f,g,b flat) can be used on any chord of a basic blues in C.
The use of the blues scale is by no means restricted to blues itself, it can be used anywhere on any chord, to taste (!!!). And in the case of the blues scale of the key of a section or composition: on any sets of chords in that section or composition that naturally form within the key. Sure, there will be harmonic conflicts, but no jazz within tension!
Harmonious
Any group of five adjacent notes in the circle of fifths are fully harmonious and forms a pentatonic sequence starting on one note and following the circle four other notes clockwise (which then have to be put in the order they have within the range of one octave).
Any combination of these five notes will sound harmonious (meaning it doesn’t create much tension; they fit well together). You can easily test this as the black keys on a piano keyboard are there to remind us of the existence of this ‘pentatonic paradise’ while the white keys show us what has become of it: the drama of the seven notes of the major scale that is the backbone of the Western Tonal System.
The culprits
Two notes were added to the pentatonic system to form the major scale: 4 and (maj)7 – the 7th note of the major scale (in chord symbols 7 means b7 and maj7 means the 7th note of the major scale; sorry for that.
Because both 4 and maj7 are only a semitone away from 3 and 1, unlike the harmonious pentatonic system, harmonic ‘accidents’ (conflicts) can easily occur within the major scale.
Other scales
There are countless other scales besides the major scale and the pentatonic scale. Scales are just sequences of notes in order within the range of one octave. You could invent a scale yourself if you wanted. Naturally there are minor scales and there are scales like the diminished or octatonic scale and the whole tone scale for example.
Which scale to use on what chord is a popular debate topic amongst jazz musicians, which demonstrates there aren’t always clear answers. If you really want to know; don’t look for the answers unless you also play an instrument on a decent level. It quickly becomes complex music theory which will be of lttile to no help for singing jazz. Not even improvising, as singers can’t push buttons to produce notes.
