Modulation is an important part of structure as it enables the composer to plan contrasting sections with a view to tonality. This creates variety and unity within the form.
Experiment by creating a bass part which draws the harmony to a temporary key or keys (= tonicisation). Then look at how the composer himself has harmonised the melody.
Listen to how Mozart uses tonicisation in the quotation below. He colours the melody by giving the expression a lift towards the middle of the phrase. The quotation comes from the opening movement of his Piano Sonata (K.331). Figure 1 shows the melody alone.
Fig. 1
Sonata in A
Mozart
tonic = A major
tonicisation in E major (i.e. dominant A major)
Fig. 2
The D# in the bass part modulates the harmony to the key of E major for half a bar, therefore is said to tonicise rather than modulate, as the harmonic change occurs only for a short while.
In order to modulate completely the composer must confirm the new key in a number of ways. The new key must be prepared and confirmed as the new tonic. The usual modulations during the Baroque and Classical periods were:
Tonic to |
dominant |
Tonic to |
subdominant |
Tonic to |
relative minor |
Tonic to |
dominant of the dominant |
Compose an original piece of approximately 4-8 bars for string quartet. You should attempt to use harmony which: