The structure of rhythm threes

lossius · April 21, 2015, 10:46am

Hi,

I’m trying to understand the structure of OM rhythm trees expressed as nested lists. I have broken down the following rhythm three:

( ( ( (4 8) ( ( 4 (1 1 1 1) ) ) ) ( (4 8) ( (4 (1 1 1 1) ) ) ) ( (4 8) ( (4 (1 1 1 1)) ) ) ) )

in the following gist file in order to understand what each of the parentheses means:

gist.github.com

https://gist.github.com/lossius/6d8c0c03e4ac50de18be

gistfile1.txt

// A: Everything...
(
  ?                       // B: The number of bars. Question marks asks OM to figure out for itself.
  // C: Now comes all of the bars
  (
    // D: The first bar
    (
      (4 8)               // E: Beat division in this bar - required for each bar
      (                   // F: Why is this paranthesis needed, what does it represent?
        (

This file has been truncated. show original

I believe I have figured out most of it, but what is the purpose of the parenthesis associated with the “F” comment?

Thanks,
Trond

haddad · April 21, 2015, 11:19am

Hi Trond,

The structure of the RT (rhythm trees) is like so :

RT = (D S)
D being duration, expressed as a ratio or number (except for the measures excetionaly they aare simple lists in the form 4/4 = (4 4)
S is a List of subdivisions integers or an RT

In your case , ( (4 8) ( (4 (1 1 1 1) ) ) ) this is like so (D (RT)) => (D ((D S)) (D ((D (i i i i))))
but this also works ( (4 8) (1 1 1 1)) which wields the same rhythm and is (D S) decomposed so : (D (i i i i))

So the parenthesis in your F example represent the list of S where you have an RT meaning (D ((D S))
Hope this helps.
Will post soon an old article about this representation .

Best
K

lossius · April 21, 2015, 3:07pm

Thanks, Karim,

This was enough to get me going with some patches that starts off simple, and then add more nested rhythm trees and study the result in voice. I’ll help a student with this in a few days, and by the time I’ve explained him, I hopefully understand it quite well myself…

Best,
Trond