[LAD] [LAU] from 4 to 400 Hz

Robin Gareus robin at gareus.org
Tue Jul 19 01:17:55 UTC 2011


On 07/19/2011 02:45 AM, pshirkey at boosthardware.com wrote:
>> 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...?
> 

The SuperCollider one-liner that Bernardo posted is actually brilliant.

robin



More information about the Linux-audio-dev mailing list