sigmatrio.blogg.se - Turn soundbyte into shepard tone

#Turn soundbyte into shepard tone series

In his book Gödel, Escher, Bach: An Eternal Golden Braid, Douglas Hofstadter explains how Shepard scales can be used on the Canon a 2, per tonos in Bach's Musical Offering (called the Endlessly Rising Canon by Hofstadter) for making the modulation end in the same pitch instead of an octave higher.

Zajac, a Shepard tone accompanies the ascent of an analogous Penrose stair. Risset has also created a similar effect with rhythm in which tempo seems to increase or decrease endlessly. When done correctly, the tone appears to rise (or fall) continuously in pitch, yet return to its starting note. Jean-Claude Risset subsequently created a version of the scale where the tones glide continuously, and it is appropriately called the continuous Risset scale or Shepard-Risset glissando. The illusion is more convincing if there is a short time between successive notes (staccato or marcato instead of legato or portamento). The scale as described, with discrete steps between each tone, is known as the discrete Shepard scale. Similar to a barber's pole, the basic concept is shown in Figure 1.

#Turn soundbyte into shepard tone series

The acoustical illusion can be constructed by creating a series of overlapping ascending or descending scales. According to Shepard, "(.) almost any smooth distribution that tapers off to subthreshold levels at low and high frequencies would have done as well as the cosine curve actually employed.") a raised cosine function of its separation in semitones from a peak frequency, which in the above example would be B 4. (In other words, each tone consists of two sine waves with frequencies separated by octaves the intensity of each is e.g. The twelfth tone would then be the same as the first, and the cycle could continue indefinitely. The two frequencies would be equally loud at the middle of the octave (F ? 4 and F ? 5), and the eleventh tone would be a loud B 4 and an almost inaudible B 5 with the addition of an almost inaudible B 3. The next would be a slightly louder C ? 4 and a slightly quieter C ? 5 the next would be a still louder D 4 and a still quieter D 5.

As a conceptual example of an ascending Shepard scale, the first tone could be an almost inaudible C 4 (middle C) and a loud C 5 (an octave higher). Overlapping notes that play at the same time are exactly one octave apart, and each scale fades in and fades out so that hearing the beginning or end of any given scale is impossible. The color of each square indicates the loudness of the note, with purple being the quietest and green the loudest. Each square in the figure indicates a tone, with any set of squares in vertical alignment together making one Shepard tone.