Audio: doubling (0:08)
doubling plays a solo melody C-A-A-E on a recorder then repeats it accompanied by an eight-piece jazz combo. The individual instruments in the combo play the same melody notes in unison or octave with the original, except for the piano and the guitar, which play the intervals CA and AE in the first and second bar respectively. The doubling figure shows the score.
Doubling is the process of repeating an individual part.
A doubled part in harmony is the equivalent of a repeat note in melody. A doubled part is the same note played twice simultaneously, a repeat note is the same note played twice sequentially.
Any note is doubled by repeating it in unison or at the octave.
Doubling is problematic. There is even some debate whether doubling constitutes harmony. For example, if two people sing or play the same melody an octave apart, is that two part harmony? We say yes, others say no.
In harmony, a chord is classified according to the number of notes that differ. Doubled notes are ignored. All that matters is which notes differ, not how many repeat notes there are. A chord can contain any number of doubled unisons and octaves, but its nature, the quality of the chord, remains unchanged.
Doubling matters in writing harmony. A part that is doubled is usually notated as such. However, a score may be notated with a chord name or number that indicates the notes that the chord contains but leaves it up to the performer to decide whether to double or triple a note. A chord with three notes, CEG for example, is a C major chord. The chord may be played on a guitar using just three strings, or on four strings with a doubled octave, or on five strings with two doubled octaves, or on all six strings with either three doubled octaves or a tripled octave and a doubled octave. The chord is still the same chord, C major, and it only contains three notes that differ.
It is easy to get confused by part terminology, because of doubling. The best way to regard the number of parts in a piece of music is as a maximum limit to the number of simultaneous and differing notes that can be played at once. Four part harmony, for example, has four different notes at some point in the music. At other times it might contain three different notes and one doubled note, two notes and two doubles or a quadrupled single note.
Doubling is an extremely effective weapon and its consequences are far-reaching. Any part can be doubled or trebled or quadrupled without affecting the harmony. There is absolutely no problem writing two part harmony as in doubling, doubling as many notes as you like and arranging for the lot to be played by a jazz combo or a symphony orchestra or sung by a duet or a massed choir. The amplitude and the timbre will differ, of course, but it is still only two part harmony at heart. Now that is power.