[LAD] [LAU] from 4 to 400 Hz

pshirkey at boosthardware.com pshirkey at boosthardware.com
Tue Jul 19 00:45:12 UTC 2011


> On 07/18/2011 04:02 AM, pshirkey at boosthardware.com wrote:
>>> On 07/17/2011 10:41 AM, Rustom Mody wrote:
>>>> On Sun, Jul 17, 2011 at 1:21 PM, Philipp Überbacher
>>>> <hollunder at lavabit.com>wrote:
>>>>
>>>>> Excerpts from Rustom Mody's message of 2011-07-17 05:33:44 +0200:
>>>>>> I am preparing to give a talk on the wider ramifications of music.
>>>>>> One of the things I wish to demonstrate is that things that look
>>>>> different
>>>>>> are merely analogs but at different scales.
>>>>>>
>>>>>> eg if something vibrates at 400Hz we hear a sound of A-flat. If it
>>>>>> 'vibrates' at 4 Hz we hear a beat.
>>>>>> In the same analogy a 2 vs 3 poly-rhythm (should?) change to a do-so
>>>>> chord.
>>>>>> And so on.
>>>>>
>>>>> I suggest you do some experiments before you give a talk. At 4 Hz you
>>>>> won't be able to hear anything, you won't even be able to reproduce a
>>>>> 4 Hz sound with common speakers.
>>>>>
>>>>
>>>> You took me quite literally,  [I did put the vibrate into quotes :-) ]
>>>> Let me spell out the experiment in more detail:
>>>> Say I have a rhythm in 4/4 time -- 4 even quarter notes, bar repeating
>>>> every
>>>> second played by say a click. [What kind of click I am not very sure;
>>>> sharp
>>>> with few harmonics would be best I expect]
>>>
>>> Exactly. Just take a short audio-sample (aka grain) and trigger it
>>> repeatedly. Increase the trigger freq. (aka grain-speed) from 4 Hz ->
>>> 400Hz.
>>>
>>> Search the net for granular-synthesis. Your use-case is not the typical
>>> grain-synth application, but the principle is the same.
>>>
>>>> Now if there were some (realtime) way of sliding the tempo from 1 sec
>>>> to
>>>> millisec I expect the separate clicks would vanish into a hum at some
>>>> stage.
>>>>
>>>> This (and other such experiments) is what I want to demo.
>>>> Ive started looking at chuck.
>>>> How does it compare with puredata?
>>>>
>>>
>>> It's a bit of an apples vs oranges question.
>>>
>>> the main difference: Chuck you program in text, pure-data you
>>> graphically connect "objects" (if you know Max/MSP: pure-data is
>>> similar).
>>>
>>> AFAIK, Chuck does not offer GUI elements - you'll need to implement the
>>> slider via OSC or use a "text slider".
>>>
>>>>>> Is there some kind of software where I can make a 4 Hz beat and pull
>>>>>> a
>>>>>> slider or a freq text box entry until it sound like a A-flat note?
>>>>>
>>>>> puredata springs to mind, it's easy to use and has everything you
>>>>> need.
>>>
>>> Indeed. Though chuck, supercollider, csound,... could all do the trick.
>>>
>>> If you know neither of those. Pure-data is probably the easiest to get
>>> started with.
>>>
>>> http://www.timvets.net/video/grains.php will do what you want with Pd.
>>>
>>
>>
>> I'm not sure that does what he wants. He asked for a tool that takes an
>> existing signal/tone and then down tunes it. What you are suggesting
>> creates an emulation of that process but generates a completely new
>> signal/tone.
>>
>> It would achieve a similar sound but is functionally quite a different
>> process.
>
> You are right or course. It's not modeling the desired effect correctly;
> Yet it's close enough and much more robust and convicing for a Demo.
>
> Actually http://www.sonicvisualiser.org/ may be the tool of choice.
> Here's a video where it is used to slow down some Bach so that you can
> hear the "beating/pulsing" introduce by equal-temperament tuning:
> http://www.youtube.com/user/mcldx#p/a/u/0/uOOhvw89jc4
>


That's an interesting feature of that tool. I was not aware of that
functionality.  It appears to work on the time domain not the
amplitude/phase of the signal. I assume as it uses a similar code base to
librubber band to achieve that functionality.

IIRC,  It is still not quite doing what the original request appeared to
be asking for.  i.e. down tuning an existing signal. ( He didn't require
time adjustment )

Would it just be a case for a pitch shifter with a automation fade curve
sone in Ardour/qtractor, etc...?



--
Patrick Shirkey
Boost Hardware Ltd









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