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Inspired by Marc Evanstein video "The Rythm of The Primes"
Link: https://www.youtube.com/watch?v=8x374slJGuo

This program will iterate over natural numbers, playing chords
based on which prime divides given number. This results in
following execution:

step: 2 3 4 5 6 7 8 9 10
      1   1   1   1    1
        2     2     2
	          3          3

where each index corresponds to specific note from scale.
Assuming scale [c,d,e] example above would be

step: 2 3 4 5 6 7 8 9 10
      c   c   c   c    c
        d     d     d
	          e          e

which would resolve into:

play c d c e (c & d) c d (c & e)

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Length := 40,

cmajor := (c,d,e,f,g),
scale := reverse cmajor,
primes := nprimes (len scale),
indicies := up (len scale),

oct 3,
len (1/16),

for (2 + up Length) ( i |
	play (chord scale[indicies[i % primes == 0]]),
),