Secondary dominant (also
applied dominant,
artificial dominant, or
borrowed dominant) is an
analytical label for a specific
harmonic device that is prevalent in the
tonal idiom of
Western music beginning in the
common practice period. In the tonal idiom, a song or piece of music has a tonic note and chord, which is based on the root of the key that the piece is in. The most important chords in a tonal song or piece are the
tonic chord (labeled as I in
harmonic analysis) and the
dominant chord (V). In the key of C major, the tonic chord is C major and the dominant chord is G.