When two or more voices in a song follow the same rhythm and move by the same interval, thus causing a parallel motion of the voices, it is referred to as Organum. Depending on the intervals between the voices, this can give rise to a rich and interesting effect.
For today’s experiment, I decided to create an organum example in Opusmodus software. I chose the song Mary had a little lamb…
First, let us see the MusicXML rendering of the song in a single voice:
Single voice
Next, the same song is played in three voices – Base (as given), a Major 3rd below and a Perfect 5th below the base. Here is the changed rendering:
Three voices
Creating this in Opusmodus is straightforward. The base pitches are transposed by the required interval to get new pitches. The code is shown below.
Opusmodus code
Here is the corresponding MIDI output. Here is the source code.
Enjoy!
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