OpenMusic Tutorials
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Tutorial 18: Generation of a note sequence by interpolation between two
chords
Topics
Using random elements and interpolation to generate a sequence of notes between two harmonic areas.
Key Modules Used
interpolation, omloop,
repeat-n, flat, Chord,
Chord-seq
The Concept:
In this tutorial as in previous ones, we will use randomly generated notes from particular chords to construct a sequence. This time, however, these chords are the result of an interpolation between two seed chords we choose. The first chord is in the lower register, and the second is in the upper register. The result of the interpolation will be an ascending sequence of chords and so will be the general tendancy of our generated note sequence.
The Patch:
We have choosen two chords of same density (i.e same number of notes) in Chord (A) and Chord (B).
The module interpolation (C) will interpolate between
these two chords using n steps. In our example above we have chosen to
create 12 steps (chords A and B included). The last argument of interpolation
defines a curve for the calculation. A curve of 1 is linear, meaning that the
arithmetic midpoint of the interpolation will fall exactly 50% of the way
through the steps. In a non-linear interpolation specified by values smaller
than 1 (but greater than 0) or greater than 1, that midpoint will be displaced
towards the front or back of the sequence. This is easier to understand if you
can see it. Open the Chord-seq at (D) and check out the
interpolation with _curve_ of 1.0:
Now, replace the _curve_ argument of interpolation
with .3 and evaluate. Notice that the intervals between chords are greater at
the beginning of the sequence. Now replace _curve_ with 1.7 and reevaluate.
Notice how the large intervals are now towards the end of the sequence. Reset
_curve_ to 1.0.
In order to apply the same process as in Tutorial 16, (picking n random
samples from each chord of the interpolation) we will use
omloop (E):
In listloop will enumerate the elements of our
interpolation one by one for each repetition of the loop. nth-random will randomly choose one note of each of these chords. Connecting
nth-random’s output to a repeat-n
module will repeat this n times on each chord. Notice that
repeat-n’s second input is getting data from an additional
input that we named _n-samples_ in order to choose the number of times we
want to sample each chord from outside omloop’s editor window (in our example
it is 4 notes per chord, see the general patch). All results will be collected
by collect and ouput by finally.
As in the last tutorial, the output of omloop will be a list
of lists equivalent to a list of chords when plugged into Chord-
seq. In order to have a sequence of notes instead of
chords, we have to flatten the list with the function flat.
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