Audio: multipart parallel (0:08)
multipart parallel plays parallel harmony in three parts. The multipart parallel figure shows the score:
Parallel harmony can easily be extended from two to three parts. All that needs to be done is to make a third copy of the original and transpose it by a different interval to the second copy. The parallel melodies are all clones of the original, they have the same pattern of notes and the same rhythm. The only difference is that the pitch of each parallel melody is higher or lower than the original.
There are a few simple decisions to make in multipart parallel harmony. Yet these decisions will produce plenty of options to experiment with. The principal one is which interval or intervals to use to write the parallel melodies. Then there is the possibility of using inversions. Finally, any of the melodies can be transposed up or down an octave.
Parallel thirds are a popular choice in multipart parallel harmony. At a rough guess over 50% of popular music harmony is written using parallel thirds because they are so easy to write and so versatile. This is because two consecutive thirds constitute a fifth so writing parallel thirds and using inversions is a method for creating parallel fourths and fifths as well as parallel thirds and sixths. Parallel seconds and parallel sevenths are also an option although much less common than parallel thirds.
Parallel harmony in four or more parts is as easy to write as it is in two and three parts. An easy option is to double one of the three parts at the octave to create the fourth part.
Multipart parallel harmony is sometimes called planing.