[LAU] from 4 to 400 Hz

Robin Gareus robin at gareus.org
Mon Jul 18 11:07:20 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

ciao,
robin


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