[Smt-talk] accelerandi-pieces

[JAY RAHN]

Some of the better urls for Risset accelerandos and Shepard
tones are as follow (the Acoustical Society of America Webpage wasn’t working a
few minutes ago): 

  

http://swiki.hfbk-hamburg.de:8888/MusicTechnology/uploads/826/Risset_accelerando_beat1.mp3 

  

http://www.netalive.org/tinkering/shepard-effect/ 

(despite the wrong note early in the series) 

  

The effects are easier to realize by means of
electroacoustic sound production than by acoustic instruments. They involve
gradually reducing the intensity of certain events while increasing the
intensity of others. For descending Shepard tones the octaves above the loudest
frequencies in individual spectra are made louder while the loudest frequencies
are made softer. For ascending Shepard tones, the octaves below the loudest
frequencies are made louder while the loudest frequencies are made softer. For
Risset accelerandos, the loudest pairs of tones become softer and their time
intervals become shorter while the longer time intervals of softer pairs of
tones become correspondingly shorter and their tones become louder, so that their
prominence gradually replaces the prominence of the originally louder pairs,
just as softer parts of Shepard-tone spectra replace the originally loudest
part.  

Each can be non-illusory if one attends to two parts of the
texture simultaneously: 2 registers of the individual tones’ spectra for
Shepard tones; 2 near periodicities for the Risset accelerandi.

Both are logically non-paradoxical if ‘at least as high as’
and ‘is at least as short as’ are non-transitive.

  

Jay Rahn

York University (Toronto) 





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