modulations (under construction)
One of the most important principles of a prelude is that it ends in the same key as it started. This does not prevent the pianist from performing modulations within the prelude itself.
However, there is also another type of prelude that has a specific function, called a modulating prelude or simply modulation. This type of prelude is used to make a connection between two repertoire pieces with different keys.
In his publication The Art of Preluding, Op. 300 (1833) Carl Czerny (1791-1857) provides different series of chords for modulations:
Carl Gottlieb Hering (1766-1853) provides almost 1000 'ausweichungen' in his Praktische Preludierschule (ca.1812).
MODULATION SYSTEMS
Rather than using pre-existing chord sequences to find a new key, it is more interesting to understand the systems of modulation. In his publication Modulations (ca.1888), Bernhard Rollfuss (1837-1904) gives a clear view on some of the possible systems.
One of these systems is modulation via a diminished chord immediately followed by the dominant fourth-sixt chord in the new key.
Some more interesting publications regarding modulations.
Bernhard Rollfuss (1837-1904)
Modulations (ca.1888)
Salomon Jadassohn (1831-1902)