9/23/2023 0 Comments Shepard tone illusion![]() They're all still playing the same pitch class, but at different octaves. When they reach the G of the scale, the trumpet drops down an octave, but the horn and tuba continue climbing. they all start playing C's, but their notes are all in different octaves. They all start to play a repeating C scale (C-D-E-F-G-A-B-C) in their respective ranges, i.e. The illusion is more convincing if there is a short time between successive notes ( staccato or marcato instead of legato or portamento).Īs a more concrete example, consider a brass trio consisting of a trumpet, a horn, and a tuba. The scale as described, with discrete steps between each tone, is known as the discrete Shepard scale. (More accurately, each tone consists of ten sine waves with frequencies separated by octaves the intensity of each is a gaussian function of its separation in semitones from a peak frequency, which in the above example would be B(4).) The thirteenth 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#), and the twelfth 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. ![]() Escher's lithograph Ascending and Descending) or a barber's pole, the basic concept is shown in Figure 1.Įach square in the figure indicates a tone, any set of squares in vertical alignment together making one Shepard tone. Similar to the Penrose stairs optical illusion (as in M.C. Hope you don’t need to go anywhere for the next 10 hours.The illusion can be constructed by creating a series of overlapping ascending or descending scales. ![]() You have to believe composer Koji Kondo took some notes from Roger Shepard when he composed this soundtrack. The exception to this rule is that if an overtone is relatively louder than the fundamental tone, like in some bells and organs, that frequency may be heard as the “note.” That also helps explain why we hear the melody in this illusion sliding up like a barber pole without noticing the incoming lower tone.Įnough science, time for a fun example of Roger Shepard’s illusion: the Super Mario 64 endless stairs. The higher frequencies (called overtones) affect us more subconsciously by giving each note its own sonic “fingerprint” called timbre. We usually consciously perceive only the lowest (and often loudest) frequency, called the fundamental frequency. So we wrap them in a neat little package we call a note. Actually, almost all musical tones contain more than one frequency, but our brains would explode if we had to process all of them at once. You might be wondering why these tones in higher octaves seem hidden to you at first. Since our brains love continuity and pattern, we follow the melody up into the next octave when replaying the sequence. So why does this work? In this video, there are actually multiple octaves playing at the same time, like red stripes on a barber pole. Do you hear the tone continue to creep up? ![]() Play the video below, and then replay it. I think of the Shepard tone illusion as the musical equivalent of the infinite staircase.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |