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Function: polygon-rhythm


Rangarajan

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Hi,

I am trying to understand the polygon-rhythm function, but having some difficulty with the finer details.

 

The expression (polygon-rhythm 5 8 4) returns 8 points (randomly generated) like this:
=> (-1/8 -1/8 1/8 1/8 1/8 1/8 1/8 -1/8)

 

Likewise, (polygon-rhythm 5 16 4) returns 16 points:
=> (1/16 -1/16 -1/16 -1/16 1/16 -1/16 -1/16 -1/16 1/16 1/16 -1/16 -1/16 -1/16 -1/16 -1/16 1/16)
This: (polygon-rhythm 3 16 8) also returns 16 points:
=> (-1/16 -1/16 -1/16 -1/16 -1/16 1/16 -1/16 -1/16 1/16 -1/16 -1/16 1/16 -1/16 -1/16 -1/16 -1/16)

 

What is the role of the first and 3rd arguments to this function?

Next: What does the keyword argument :legato achieve?

The expression (polygon-rhythm 5 8 4 :legato t) returns:
=> (-1/8 1/8 1/4 1/4 1/8 1/8)

 

I can see that the result has only 6 elements, instead of 8. What is going on?

I went through the documentation, but still couldn't understand these points.

 

Regards,

Rangarajan

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After posting the above message, I happened to watch the video "How-to in 100 sec" Part 4. The author clearly says that the first argument indicates the number of "beats". I am able to verify this. So, the expression (polygon-rhythm 5 8 4 ) returns 8 points and 5 of them are beats while the remaining 3 are rest. 

 

I still do not know the answer for the other two questions I asked:

1) What is the third argument for?

2) What is the impact of :legato keyword?

 

Regards,

Rangarajan

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You are correct, the third argument represents the starting point on the circle. It makes sense in terms of visualisation, but how does it affect the values returned by the expression?  

 

Sorry, I still do not understand :legato. In your example, you have said that legato removes rests and ties the notes. Even then, how does "s -s s s" become "e s s"? If I remove the rest, the list becomes "s s s" and then how does tie happen?

 

Thanks for your help.

 

Regards,

Rangarajan

 

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The :legato T in POLYGON-RHYTHM function use the LENGTH-LEGATO function:
 

LENGTH-LEGATO inverts length-rests to a length-note and adds the sum of the rests in sequence to the previous length-note.

 

(length-legato '(1/8 -1/16 1/16 -1/12 2/12 2/20 -3/20 -1/8 3/8))
=> (3/16 7/48 1/6 3/8 3/8)

(length-legato '(-1/8 -1/16 1/16 -1/12 2/12 2/20 -3/20 -1/8 3/8))
=> (-3/16 7/48 1/6 3/8 3/8)

(length-legato '((-1/8 -1/16 1/16 -1/12) (2/12 2/20 -3/20 -1/8 3/8)))
=> ((-3/16 7/48) (1/6 3/8 3/8))

 

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The 3rd argument is the start point (1st point).
Evaluate each of the expressions a few times.

(circle-rhythm-plot (polygon-rhythm 3 16 0) :points 16)
(circle-rhythm-plot (polygon-rhythm 3 16 1) :points 16)
(circle-rhythm-plot (polygon-rhythm 3 16 2) :points 16)
(circle-rhythm-plot (polygon-rhythm 3 16 3) :points 16)

 

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