[sdiy] Filtering for chromatic scale frequencies?

Tom Wiltshire tom at electricdruid.net
Thu May 31 12:53:55 CEST 2018


+1 agree. I’d be inclined to do it the “other way up” too. Rather than trying to cut out non-chromatic frequencies in-between notes (hard) I’d look at using resonant peaks to boost chromatic frequencies (easier) and then compensate for the boost by lowering the overall level.

Comb filters is a nice idea, since you’d get all the octaves for free. You’d need 12 chromatically tuned delay lines.

> On 31 May 2018, at 07:53, David G Dixon <dixon at mail.ubc.ca> wrote:
> 
> I'm pretty sure you can filter for frequencies in the harmonic series of a
> certain fundamental...?  For example, if you sweep a high-Q bandpass filter
> across a sawtooth signal, you should be able to pick out the various
> harmonics up to the point where they cease to have any amplitude.  That
> probably doesn't help you though.
> 
> On the other hand, a bunch of peaky bandpass filters carefully tuned to the
> chromatic scale should do what you want somewhat.  Would that be a comb
> filter (somebody else here with stronger filter-fu will know the answer).
> 
>> -----Original Message-----
>> From: Synth-diy [mailto:synth-diy-bounces at synth-diy.org] On 
>> Behalf Of Mike Beauchamp
>> Sent: Wednesday, May 30, 2018 10:49 PM
>> To: synth-diy at synth-diy.org
>> Subject: [sdiy] Filtering for chromatic scale frequencies?
>> 
>> This might be bit of a strange one.. I'm wondering if there's 
>> any way to filter an audio signal to favour frequencies that 
>> are within the chromatic scale?
>> 
>> So, sort of like "autotune" - but instead of correctively 
>> altering the pitch of 'wrong' notes, the filter is just 
>> lowering their amplitude significantly.
>> 
>> Mike
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