Generator-offset property: Difference between revisions
No edit summary Tags: Mobile edit Mobile web edit |
|||
| Line 8: | Line 8: | ||
The [[Zarlino]] (3L 2M 2S) JI scale is an example of a GO scale, because it is built by stacking alternating 5/4 and 6/5 generators. The 7-limit version of [[diasem]] (5L 2M 2S) is another example, with generators 7/6 and 8/7. | The [[Zarlino]] (3L 2M 2S) JI scale is an example of a GO scale, because it is built by stacking alternating 5/4 and 6/5 generators. The 7-limit version of [[diasem]] (5L 2M 2S) is another example, with generators 7/6 and 8/7. | ||
== Mathematical definition == | |||
More formally, a cyclic word ''S'' (representing the steps of a [[periodic scale]]) of size ''n'' is '''GO''' if it satisfies the following properties: | More formally, a cyclic word ''S'' (representing the steps of a [[periodic scale]]) of size ''n'' is '''GO''' if it satisfies the following properties: | ||
# ''S'' is generated by two chains of stacked generators g separated by a fixed offset δ; either both chains are of size ''n''/2, or one chain has size (''n'' + 1)/2 and the second has size (''n'' − 1)/2. Equivalently, ''S'' can be built by stacking a single chain of alternants g<sub>1</sub> and g<sub>2</sub>, resulting in a circle of the form either g<sub>1</sub> g<sub>2</sub> ... g<sub>1</sub> g<sub>2</sub> g<sub>1</sub> g<sub>3</sub> or g<sub>1</sub> g<sub>2</sub> ... g<sub>1</sub> g<sub>2</sub> g<sub>3</sub>. | # ''S'' is generated by two chains of stacked generators g separated by a fixed offset δ; either both chains are of size ''n''/2, or one chain has size (''n'' + 1)/2 and the second has size (''n'' − 1)/2. Equivalently, ''S'' can be built by stacking a single chain of alternants g<sub>1</sub> and g<sub>2</sub>, resulting in a circle of the form either g<sub>1</sub> g<sub>2</sub> ... g<sub>1</sub> g<sub>2</sub> g<sub>1</sub> g<sub>3</sub> or g<sub>1</sub> g<sub>2</sub> ... g<sub>1</sub> g<sub>2</sub> g<sub>3</sub>. | ||
| Line 22: | Line 22: | ||
An ''m''-GO scale can be interpreted as a scale in a rank-(''m'' + 2) [[regular temperament]], with basis p (period), g, δ<sub>1</sub>, ...,δ<sub>''m''</sub> (though the specific tuning used may be of lower rank). | An ''m''-GO scale can be interpreted as a scale in a rank-(''m'' + 2) [[regular temperament]], with basis p (period), g, δ<sub>1</sub>, ...,δ<sub>''m''</sub> (though the specific tuning used may be of lower rank). | ||
== Conventions used on this page == | == Conventions used on this page == | ||
* Non-italicized Latin variables refer to interval sizes, for example step sizes. | * Non-italicized Latin variables refer to interval sizes, for example step sizes. | ||