[sdiy] samplers & pitch shifting

Scott Gravenhorst music.maker at gte.net
Sun May 13 20:12:20 CEST 2018


Yes it does and I realized you didn't want that after I hit send.  Not sure how I would handle
stretching or squishing the output waveform to conform to maintain the original length.

The frequency shifter will change the harmonic structure because frequency shifting will add or
subtract the same number of Hertz from all of the components (partials) in the waveform.  The
resulting signal will have a somewhat different sound because (in a periodic wave) the harmonics
won't be integer multiples of the fundamental.

Tim Ressel <timr at circuitabbey.com> wrote:
>I think I saw that in the Chamberlin book. But doesn't that change the 
>effective length of the sample?
>
>How does Auto-tune do it?
>
>--tr
>
>
>On 5/13/2018 9:20 AM, Scott Gravenhorst wrote:
>> Hi Tim and list,
>>
>> I'm no expert, but I know that if you raise the pitch of a band limited sample, you
>> can still have aliasing unless some technique is used to prevent it.
>>
>> What I've done is to use fractional samples taken from the original wave and
>> interpolate.  I've never gone beyond linear interpolation and have not found problems.
>>   This goes for whether it's pitch down or pitch up (assuming that the band limit is at
>> a low enough frequency cutoff to prevent alias artifacts.
>>
>> I can't say anything about the Bode as I've not yet studied it.
>>
>> Tim Ressel <timr at circuitabbey.com> wrote:
>>> Hi,
>>>
>>> Forgive me if I've asked this before. I can't seem to get my head around
>>> this. I'm told if you make for example a drum machine that uses samples
>>> you HAVE to be able to change the pitch. How is this done? The pitch has
>>> to change but the sample length stays the same. Are we talking about a
>>> digital version of a Bode pitch shifter?
>>>
>>> -- 
>>> --Tim Ressel
>>> Circuit Abbey
>>> timr at circuitabbey.com
>>>
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>> -- ScottG
>> ________________________________________________________________________
>> -- Scott Gravenhorst
>> -- http://scott.joviansynth.com/
>> -- When the going gets tough, the tough use the command line.
>> -- Matt 21:22
>>
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>
>-- 
>--Tim Ressel
>Circuit Abbey
>timr at circuitabbey.com
>
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-- ScottG
________________________________________________________________________
-- Scott Gravenhorst
-- http://scott.joviansynth.com/
-- When the going gets tough, the tough use the command line.
-- Matt 21:22



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