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Physics 371 March 14, 2002

Physics 371 March 14, 2002. Acoustics for Musicians. Scales (end) names of intervals transposition the natural scale the tempered scale meantone tuning. The Natural Scale. bugle, bach trompet, natural horn etc. 1 2 3 4 5 6 7 8 9 10

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Physics 371 March 14, 2002

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  1. Physics 371 March 14, 2002 Acoustics for Musicians • Scales (end) • names of intervals • transposition • the natural scale • the tempered scale • meantone tuning

  2. The Natural Scale bugle, bach trompet, natural horn etc. 1 2 3 4 5 6 7 8 9 10 C C G C E G (Bb) C D E example: find tones of horn in G

  3. the problem of transposition how many keys do I need to retune? what if I don’t retune? what about adding more keys to the keyboard?

  4. Help in visualizing scales: octave octave octave C D E F G A B C 1 x x x • equal musical intervals - equal frequency ratio • 44on a “multiplicative” number line (=log scale) equal ratios are equidistant • advantage: in graphs below equal intervals have same length 1 1.5 2 3 4 6 8 12 fifth 2 JUST x Triad

  5. 3/27/2001 The Tempered Scale Octave divided into 12 equal intervals Semitone ratio x: x12 = 2 x = 1.05946…. How to calculate tempered frequency ratios: Example on blackboard: fifth - 7 semitones major third - 4 semitones

  6. Tempered Scale - good or bad? all 12 halftone intervals are identical (100 cent) solves problem of transposition how good (“exact”) are the tempered intervals? the fifth is good (called “perfect” by musicians) 700 cent but should be 702 cent ratio = 1.498 major third is sharp!400 cent instead of 386 cent 1.26 instead of 1.25 example: 480+605 Hz 480+600 Hz minor third is flat!300 cent 315 cent fourth is good 498 cent instead of 500 cent

  7. Meantone tuning - another interesting compromise 1. Use just major third, divided into two equal intervals 2. This defines a wholetone interval - how many cents? (answer: 193.2 cents) 3. five whole tones use up 966 cents of the octave 4. Problems remain - see homework # 7

  8. What do musicians not bound to a fixed scale (e.g unfretted strings) actually play? Measurements on violin soloists (Green 1937) Minor third mean 296 cents (range 289-301) Major third 406 400-417 (just: 386!!) Fifth 708 692-731 (just: 702!!) Maybe one likes what one is used to…… Evidence: originally, tempered scale sounded bad now just or meantone sounds out of tune

  9. Other cultures - other scales…... Example: measurements on Burmese Xylophone show that wholetones are smaller and half tones larger than Western scales, tending toward seven almost equal steps. Similar scales are used in tuning of the Burmese harp. Demo: scale with seven equal intervals within octave. Tuning matters mostly in polyphonic music - Only when playing cords is consonance the main issue Became wide spread only in late Renaissance (after 1600)

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