Thursday, 25 March 2010

Tone Rows And Rhythm

In today's post we're looking at another relatively simple example that introduces two more ideas:
  • working tone rows (serialism)
  • working with rhythm
As it's the firs time we've used this ideas in patches we'll use fairly straight forward implementations. Here's a summary of what our algorithmic composition patch will do:

1. Specify a tone row, this will always be played through in order. The tone row is specified by using pitch classes in a message that is then stored in a table, the tone row in the example patch is

11 10 7 1 3 0 2 9 6 4 8 5 though feel free to change this.

2. Specify a series of rhythms. For this we've assumed a tempo of 60BPM. So:
  • Whole note (semibreve) = 4000ms
  • 1/2 note (minim) = 2000ms
  • 1/4 note (crotchet) = 1000ms
  • 1/8 note (quaver) = 500ms
  • 1/16 note (semiquaver) = 125ms
  • 1/32 note (demisemiquaver) = 62.5ms

3. Assuming a consistent tempo of 60BPM makes working with rhythmic values easy, we don't have to stick to 60 BPM however. If we multiplied each value by 2 the tempo would be twice as quick. We've included a simple tempo multiplier slider that is connected to a multiply object:

4. We'll follow serialist principles, each note of the row is of equal importance and the tone row is played through in order. A counter counts from 0 to 11, this is connected to a tabread object that read through our tone row:

5. We can transpose the tone row to any starting pitch, play it backwards and invert it. Here, once the counter has completed we trigger a random transposition for the next play through the row, we also invert the row every other time:

6. The notes of the tone row can appear in any octave. We've included a random transposition of octaves for each note:

7. For each note we're choosing a random rhythm from our rhythm list. You can see some of the rhythms are set to 0, so if this rhythm is chosen we'll have two notes played at once:

8. Here is the final patch (click on the image to see a larger image):

I recommend creating the patch yourself by copying the layout of the screenshot, however you can also download the patch here.

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