Stretching Time...

[Kevin Moon]

Hey Stu and DIY,
My mind is set on one of these too. I don't have acess to a time stretch
function on my sampler but I'd like to build one. The way I time stretch my
samples is like this...
 First I sample a sound (let's say the vocals..."time") at an octave higher
through a pitch shifter, then I play it back an octave lower than the
original sample. The result is a much slower "time" but the TONE (correct me
if I'm wrong)  is the same as the original sample saying  "time".

>Initially I'd thought of selectively doubling up or cutting out 16bit words in
>order to expand or contract the waveform ?
I've thought of this method for stretching. Say the above "time" was only
two bits sampled at a very low clock frequency (ouch!) like the following
data...
10 11 00 (voltage wrt time) then you could stretch it to...
10 10 11 11 00 00  Is this what you mean? 

Couldn't this be accomplished by using some sort of monostable multivibrator
latch system.  Think of the mess if you wanted to sample at 44.1Khz! There
is an easier way to do this but I haven't learned about uP yet in school. 

The Kurzweil 2000 series has a Mix Beat function. I wonder if this is what
your talking about in the following...
>e.g. when stretching drum loops avoid altering the drum sound data and simply
>pad/contract the spaces between the drums.
Like musically changing the tempo.  What would happen if you sampled a jazz
drummer where there's constant cymbals throughout the loop? You would have
to use the "copy then paste per bit" method.

The problem that I'm having is...
What would happen if I time stretched a sine wave? The o/p would be simply a
lower frequency depending on the amount of time stretching desired (T=1/f).
Time stretched?? I would have to say no because what happend to my original
(here it is again) TONE? Mabey TONE=complex wavefrom analysis. Fill me in if
anyone can help me understand this situation...

BTW How do samplers playback over a range of keys? By changing the DAC's
clock...Nah sounds to easy! 

Hope this sparked some synapses,



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"Biten' your style man and they comin' out here making 
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                                                           Fab 5 Freddy
 Kevin Moon  SmToAoRnR  to.ca  moon at interlog.com 
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