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loscil

Date1997-06-27 18:49
FromJohn Francis Beahan
Subjectloscil
Can soeone clarify this statement from the manual: 

"loscil samples the ftable audio at a rate determined by kcps, then
multiplies the result by xamp.  The sampling increment for kcps is
dependent on the table's base-note frequency ibas, and is automatically
adjusted if the orchestra sr value differs from that at which the source
was recorded.  In this unit, ftable is always sampled with interpolation." 

This statement does not seem to reflect what happens when we change the kcps 
rate.  It is  acting more like a notch filter.  When we increase the rate 
we get only the higher frequency.  When we set it at a lower rate we get 
only the lower frequency(if it is really low what we get is a rumbling 
sound).

>From this statement we expect the best results to happen when we set it 
to the files sample rate.

If someone could please clarify what is exactly happening with this rate in 
the loscil generator , it would be greatly appreciated.

Thank You,

John Beahan, 
	

Date1997-06-27 19:16
FromMike Berry
SubjectRe: loscil
	loscil simply reads the file at a variable rate.  If you set the
kcps equal to the ibas, then the file is played at normal speed for the
normal length.  If you set kcps to half of ibas, the file is played at
half-speed (sounding a distorted octave down) and lasts twice as long.
kcps= 2 * ibas plays at twice speed (octave up) and lasts half as long.
This mimics the behavior of hardware samplers which assign a single sample
to multiple keys - i.e multiple frequencies.  You simply have to think of
the ratio kcps/ibas to determine the alteration from the normal speed file
playback.

Mike Berry
mikeb@mills.edu
http://www.mills.edu/PEOPLE/gr.pages/mikeb.public.html/mikeb.homepage.html