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Old 08-18-2013, 07:05 AM   #1
narinderkapur
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Question Shepard Scale?

Could anybody give me a laymans explanation of a Shepard scale? I can't seem to get my head around it, especially the octave bit.

I"m highly interested in applying it musically so any songs/pieces that have this scale used that you can suggest will be really helpful too. Links, articles, anything at all.


Thanks!

P.S.: Apologies if I've posted in the wrong forum.
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Old 08-18-2013, 07:10 AM   #2
Banjocal
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http://en.wikipedia.org/wiki/Shepard_tone#Construction

It's more a conceptual thing than something easily applied. It'd lend itself well to minimalsim or progressive music but it requires programming or a large ensemble.

Last edited by Banjocal : 08-18-2013 at 07:12 AM.
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Old 08-19-2013, 04:20 PM   #3
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I think the concept is similar to the Risset effect, there's a Risset tone generator in Audacity if you use that at all. Also I think the effect is used in the very beginning of the Collective Soul song Energy, but I could be mistaken on the difference between Shepard and Risset. Not sure how much it's used in music besides as a sort of passing effect
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Old 08-20-2013, 10:05 PM   #4
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Quote:
Originally Posted by narinderkapur
Could anybody give me a laymans explanation of a Shepard scale? I can't seem to get my head around it, especially the octave bit.

I"m highly interested in applying it musically so any songs/pieces that have this scale used that you can suggest will be really helpful too. Links, articles, anything at all.


Thanks!

P.S.: Apologies if I've posted in the wrong forum.


It is a long time since I looked into this stuff but the idea is that...

The human ear can hear basically from around 20Hz to around 20000HZ

Each frequency is heard as a different pitch. So a sound wave with a frequency of 440Hz gives us a specific pitch that we call an A.

If we double the frequency of a pitch say we get the same note an octave higher. For example 440Hz and 880Hz are both frequencies that produce a note we would call A. We hear them as the same note but the one with the faster frequency is heard as a higher "A" note and the one with the slower frequency is heard as a lower instance of the same "A" note.

If someone can hear in a range of 20Hz to 20000Hz then they would be able to hear 9 different A notes at different "pitch heights"
22.5 Hz
55 Hz
220Hz
440Hz
880 Hz
1760Hz
3520Hz
7040 Hz
14080 Hz

The idea behind the shepard scale is that the notes are produced as sine waves and all the octaves are layered on top of one another. Thus we would hear A being played in all these frequencies at the same time as one sound.

When we create a scale in this way we end up with a bunch of notes in which the "pitch height" is indiscriminate. This means that we can't tell the pitch height since all the pitch heights from the lowest to the highest are being played at the same time.

All we then have is context. The example that follows is a recording I made years ago called "indiscriminate pitch height". The first three notes you hear are A - G# - A.

This is then followed by a full A major scale A B C# D E F# G# A.

What I was doing in this experiment is exploring the effect of shepard tones. The first three notes sounds like the G# is below the A. It sounds like we are going down a half step. However exactly the same audio file was then placed as the seventh degree in an ascending scale and it then sounds like it is a major seventh above the first A tonic.

Similarly all the A notes are exactly the same audio file. The note at the start of the scale and the note at the end of the scale are from the same audio file. You could get take the first seven notes in this scale A B C# D E F# G# and loop them over and over and it would sound like a scale that is forever ascending because each note will always sound higher than the last.
Shepard Scale - Indiscriminate Pitch Height

The shepard risset rising tone is an example of this and you'll find one below. It's basically a series of the same note heard in different octaves. As we listen we hear all these pitches rise to the next octave, the highest note becomes inaudible and the lowest note comes in from being inaudible. Because each note finishes where another starts it is then looped seamlessly and the effect is a tone that appears to be continuously rising.
Shepard Risset Rising Tone

A shepard scale is basically using the tones similar to those in the first example and creating a continuously ascending (or descending) scale.

At least that is my understanding of it all.
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