[sdiy] harmonics & vibrato

[Scott Evans, Gen Mgr]

Richard,

I like your idea regarding the frequency shifter/LFO. I think this may 
be a fun place to experiment. I am also in need of a frequency shifter 
as well, so it will have to wait.

Scott
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Richard Wentk wrote:
> At 11:10 18/12/2002 +0000, Brendan wrote:
> 
>> I suppose I wondered if there might be an area under/near the finger 
>> that is
>> partially damped - somewhere between being fully stopped and freely
>> vibrating - and so any modes that have peaks in that area might be 
>> reduced
>> in amplitude, changing the timbre if the shape of the finger pad changes.
>>
>> Having said that, only energy at frequencies at the very limits of human
>> hearing (and above those limits) have peaks this close to their nodes (in
>> the millimetre scale) so as interesting a thought as it may be, it 
>> probably
>> just doesn't matter! :)
> 
> 
> No, I think it does. I've been thinking a lot about how real sounds are 
> waaaay more complicated than we think they are.
> 
> Like vibrato. Firstly real vibrato isn't a sine wave. It's going to be 
> slightly randomised wrt both pitch and amplitude. And it probably won't 
> be perfectly symmetric. And it will have a frequency curve that varies. 
> Listen to a real cellist and you can hear that their vibrato often 
> starts slow and then speeds up a little.
> 
> Secondly I'm wondering how the speed of a moving finger compares with 
> the speed of the displacement waves in a string that create the sound. 
> If they're comparable, you're going to get harmonic non-linearities 
> because the nodes won't have time to settle the way they would if a 
> fixed obstacle were damping the string.
> 
> Bottom line is you'll get interesting timbral variations that are richer 
> than just a generic fixed LFO wobble. If I had a frequency shifter to 
> hand (which I don't) I'd wonder about creating string vibrato with a 
> slightly randomised LFO driving the frequency shift amount as well as 
> VCO frequency.
> 
> If anyone does have one to hand, I'd be interested to hear how the 
> results compare with simple vibrato.
> 
> Richard
> 
> 
>