GLOSSARY in progress

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    A Moment of Symmetry is a scale that consists of: 
    1. A generator (of any size, for example a 3/2 or a fifth which is repeatedly superimposed but reduced within
    2. An Interval of Equivalence commonly called a period (of any size, for example most commonly an octave).
    3. A Moment of Symmetry is formed where each scale degree or scale unit size will be represented by no more than two sizes and two sizes only (Large = L and small = s).
    4.The relative number of L and s intervals is coprime, i.e. they share no common factors other than 1.
    5. The numerator (generator) and denominator (period) representing MOS are also co-prime.
    Wilson cited in Grady [KG]
    Noble MOS
      A special class of MOS scales generated from noble numbers which are irrational numbers “whose continued-fraction expansions end in infinitely many 1’s” (Schroeder 2009, p. 387). Wilson referred to these scales as “gold scales” because the ratios of L to s intervals eventually converge on the value Phi or the golden ratio. Noble MOS appear in the Scale Tree, Golden Horograms, Rabbit Sequence and Straight Line Patterns of the Scale Tree. [TN]
    Rabbit Sequence
      A number series that was originally suggested by Fibonacci to predict “how fast rabbits could breed in ideal circumstances” (Knott 2010) by showing how baby rabbits grow into adults and eventually have their own babies from one generation to the next. Wilson applies the same principles of the Rabbit Sequence to MOS scales in order to show how small (s) intervals become large (L) intervals, and then divide into s and L between generations. The Rabbit Sequence predicts how many L and s intervals are found in each MOS and in what order, and it also restates the fact that the relative numbers of L and s intervals in an MOS are co-prime. [TN]
    Rank
      The number of columns in a keyboard used to highlight a preferred scale subset within a larger scale array to provide the possibly most conveinent fingering. see https://anaphoria.com/xen1.pdf for example [KG]
    Scale
      An ordered set of pitches which in Wilson’s theoretical framework is conceived melodically in contrast to a harmonic structure. [TN]
    Scale Tree
      A numerical configuration devised by Wilson to represent the full spectrum of MOS scales on an infinite map of hierarchically ordered fractions. Like the Stern-Brocot tree to which it is related, fractions on the Scale Tree always appear in simplest form and in ascending order from left to right. The tree can be extended indefinitely to encompass all positive fractions but each fraction will appear only once. The Scale Tree underpins much of Wilson’s work and is essential to understanding his tuning theories, including his keyboard mapping system. Ratios on the Scale Tree represent MOS scales as well as different types of keyboards in Wilson’s system. Each of these scales and their associated keyboards are arranged into nested families that are organized hierarchically on the Scale Tree. It is often assumed that the Scale Tree is identical to the Stern-Brocot tree but Wilson includes extra information such as the decimal values of fractions as well as various noble numbers upon which the zigzag patterns on the branches of the Scale Tree eventually converge. Furthermore, Wilson explores a variety of ways to reseed the Scale Tree from different fractions. [TN]
    Secondary Moments of Symmetry
      A subset of scales derived from a ‘parent’ MOS to form a family of variations. For example, Wilson’s paper, “The Tanabe Cycle” (1998), shows how various 5-tone scales found in Japanese music can be derived from a 7-tone MOS scale. Secondary MOS are sometimes also referred to as “sub-moments”, “nested MOS” or “bi-level MOS”. [TN]
    Straight Line Patterns
      A diagram representing the infinite range of MOS scales that can be generated from an interval that varies in size over a continuum. The generating interval (which can be a rational or irrational value such as a noble number) and its superimpositions are shown as diagonal lines. Any line that can be drawn horizontally to intersect the diagonals is potentially an MOS. The Straight Line Patterns specifically show Noble MOS and ET scales as horizontal lines that correspond to the Scale Tree. The diagram is drawn to scale so that the positions of ratios from the Scale Tree are shown relative to their size. An important feature of the Straight Line Patterns is that they show the L and s interval patterns of MOS scales changing gradually until they invert across an ET line to become their opposite, i.e. an L interval becomes an s, and vice versa. [TN]
    Superparticular
      A term describing any ratio in which the difference between the numerator and the denominator is equal to 1 (Nelson n.d.), in other words, (n + 1) / n (Chalmers 1993, p. 206). [TN]

    Contributors
    [TN] Terumi Narushima
    [KG] Kraig Grady

References

Bogomolny, A 2012, Farey Series and Euclid's Algorithm, from Interactive Mathematics Miscellany and Puzzles, viewed 6 Feb 2006, http://www.cut-the-knot.org/blue/Farey.shtml.

Chalmers, J 1993, Divisions of the Tetrachord, Frog Peak Music, Lebanon NH.

Grady, K 1986, ‘Combination-Product Set Patterns’, Xenharmonikôn, vol. 9, 4 pages.

--- 1999, ‘Re: CS’, Alternate Tunings Mailing List, 4 Oct, viewed 23 Nov 2012, http://launch.groups.yahoo.com/group/tuning/message/5244.

Hero, B 2012, International Lambdoma Research Institute, viewed 3 Feb 2006, http://www.lambdoma.com.

Knott, R 2010, The Fibonacci Numbers and Golden Section in Nature – 1, viewed 7 Mar 2012, http://www.maths.surrey.ac.uk/hosted-sites/R.Knott/Fibonacci/fibnat.html.

Nelson, K n.d., Music-Science Glossary, viewed 6 Feb 2006, http://www.music-science.net/Glossary.html.

Novaro, A 1927, Teoría de la Musica: Sistema Natural Base del Natural-Aproximado, Mexico, D.F.

Schroeder, MR 2009, Number Theory in Science and Communication: With Applications in Cryptography, Physics, Digital Information, Computing, and Self-Similarity, Springer, Berlin, Heidelberg.

Wilson, E 1969-1970, Some Diamond Lattices (and Blanks), The Wilson Archives, viewed 31 Mar 2013, http://anaphoria.com/diamond.pdf.

--- 1989, ‘D’alessandro, Like a Hurricane’, Xenharmonikôn, vol. 12, pp. 1-38.

--- 1994, The Gral Keyboard Guide, The Wilson Archives, viewed 21 Mar 2010, http://anaphoria.com/gralkeyboard.pdf.

--- 1996, So-Called Farey Series, Extended 0/1 to 1/0 (Full Set of Gear Ratios), and Lambdoma, The Wilson Archives, viewed 6 Feb 2006, http://anaphoria.com/lamb.pdf.

--- 1998, The Tanabe Cycle and Parallelogram from the Tanabe Cycle, The Wilson Archives, pp. 11-12, viewed 22 Aug 2008, http://anaphoria.com/mos.pdf.

--- 2000, Diophantine Triplets of Temperament Derived Intervals, The Wilson Archives, viewed 6 Jan 2016, http://anaphoria.com/DiophantineTripletsTEMPER.pdf.

Xenharmonic Wiki 2012, MOS Scales, viewed 7 Oct 2012, http://xenharmonic.wikispaces.com/MOSScales.


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