The major scale is certainly the most important scale in music (at least for Western music) because it is used in many styles like Pop, Rock, Hard Rock, and Jazz. A large part of music theory and harmony in general is based on this scale and its construction. Here are some things that you need to know.
To improvise with a group of chords it is important to first “deconstruct” them into notes, allowing us to figure out which scales we can use for improvisation and solos. By mastering the system of harmonized scales, for both major or minor keys, we can detect whether all the chords are in the same key or if any modulations have been made.
To start with we will look at the most common C major harmonized scale, which includes the following chords: C Dm Em F G Am and B dim (diminished). Anytime we have these specific chords in a progression it will be possible to use the C major scale for improvisation.
Say you are playing a song with the chords C Am Em Dm C F and G, these are all diatonic with the C major key. So when we come to a solo section it is possible to play any notes within the C major scale and they will sound good. Just remember that often when improvising it helps to start and end on the C note. This isn't always necessary, but when you first start practicing it will help your solo fit better.
Note: On this website you will find a “chords that fit” insert. This is a list of the most common chord progressions and which notes and scales they correspond to.
Modern music is also commonly played with different minor scales. We will first talk about the natural minor scale, which is relative of the major scale. And in Blues, Rock, etc., the most used scale is the minor pentatonic scale. Finally, two other scales are used, as well as their modes: the harmonic minor scale and the melodic jazz minor.
A natural minor scale has the same notes as its relative major scale. However, we start on the sixth note, known as the Aeolian mode. Because the sixth is a minor any song using this scale will often have a sad or melancholy feel to it.
Just as we did with the major scale, by analyzing the harmonic content of a sequence of minor chords, we can figure out the scales necessary for improvisation.
For example, the chords constituting the C minor scale are Cm Ddim Eb Fm Gm Ab and Bb. Let's build the following progression: Cm Gm Fm Cm Ab Bb.
All of these chords are diatonic to the C minor key, which means we can use the notes of the C minor scale to improvise or solo with. The C minor scale is C, D, Eb, F, G, Ab, Bb. Minor keys are much more complex so we need to be careful and use the right minor scales.
The pentatonic minor is a scale of only five notes that is often used in Blues, Pop, and Rock. After the major scale the pentatonic minor is THE scale to know. It is composed of all the same notes of the minor scale above, except without the 2nd and 6th notes. It is simply made up of C, Eb, F, G, and Bb. Because it is only five notes this scale can be played in a minor, major, and dominant context, it is a very versatile scale.
The minor harmonic scale is a minor scale with a seventh major, and an interval of one and a half tones between the minor sixth and the major seventh. Instead of the Bb as the seventh, here we raise it to a B. This gives it the very recognizable sound of “middle eastern” music. In fact, this scale was once known as the Mohammedan scale.
In this scale we simply change the sixth and seventh notes to a major, giving us; C, D, Eb, F, G, A, B. This scale sometimes can be considered to be a little awkward for vocal melodies given the change on the sixth note so it is often used in jazz.
Many minor tracks are composed of chords and rhythms from various minor scales, which are in fact interchangeable. Some minor tracks of modern jazz mix the minor scales with chords taken from the Dorian or Phrygian modes. This inter-modal exchange is the principle of using chords from another scale that has the same tonic. It is like a passing modulation, facilitated by the fact that these scales have many common chords that make it possible to easily move from one to the other. For improvisation, one can use the scale from which the chord comes. And since some chords are common to the different scales, we will sometimes have several choices. Here is an example of a grid in C minor with inter-modal exchange. In this sequence of AbMaj7 Cm Dm7b5, we have two choices because these three chords are part of the harmonization of the minor natural and minor harmonic scales.
Inter-modal exchange is also possible between major and minor modes. For improvisation, we will use the same principle, namely on the scale (or the mode) from which the chord comes to improvise on it.