Since modulation is a transition from one tonality to another, it is necessary to give the concept of tonality: a scale from a certain note receiving the function of the main first step - the tonic; and a system of chords built on all seven steps of the scale
Besides the main function of tonic
, there are two additional functions: the dominant
. It is necessary to understand that the function is not a chord, but the property that tonality attaches to the chord in accordance with the scale.
Thus, each of the three functions - T, SD and D refer at least to three chords located at the steps of scale:
T - at I
, III , VI
SD - at IV
, II , VI
D - at V
I , IV and V are the main steps of three functional groups of chords. Together they form a chord pattern, called tonal cadence - in the following order: T -SD- D- T
. In C major it will be C-F-G(7) -C ; in F major : F - Bb -C(7) - F ; etc.
In tonal music there are no chords without some function; conversely, you can see that one chord can have two functions , and the knowledge of these functions helps to move from any key to any other - ie. create a modulation.
To determine the key, we look for the neighborhood of three functions SD-D-T ; however, the most representative function is the dominant
, which sooner or later inevitably leads to the tonic.
Some types of modulations.
1. The simplest is the sudden modulation: the musical fragment ends on the tonic, and you go over suddenly, without any preparation to the tonic of new key. It is not very desirable if there is a vocalist.
2. Prepared modulation: before
a new tonic you put a new dominant, or pattern SD -D from new key .
3.Modulation through a common chord for both keys; which is called - pivot
chord . For example, you need to switch from C major to Bb major. They have 2 common chords : Dm
; through each of them you can go into a new key: C - G(7) - C - F - Dm(III of Bb) - Gm(VI of Bb) - F(7)(V of Bb) -Bb.
4. There are 3 universal chords for switching from any chord to any other and key to any other - 3 diminished 7 : Bdim7 ,C dim7 ,C#dim7 , and all their inversions. Through them, you can go straight to any new tonic, dominant or subdominant; only in many cases you get them in inversions, which requires continuation in a new key to a logical final cadence.
From C major to G# minor : C - F -G -C - Bdim7 - G#m/B(new tonic) - C#m (new subdominant) - D# (new dominant)- G#m .