Archive of the former Yahoo!Groups mailing list: MOTM

There is no such thing as an analog Pitch Shifter. At least as far
as I know. I suppose one could be built if you could find a charge
coupled bucket brigade type device capable of high enough quality,
but that's unlikely. All pitch shifters are digital and break the
incoming signal into samples just like digital delays. There are
always trade offs involved in making a pitch shifter as well, as
improved pitch accuracy and improved timing accuracy are somewhat
mutually exclusive.

I think what you are really looking for is a pitch shifter which can
accept a control voltage to control the amount that the signal is
shifted in pitch. This is also difficult to accomplish. Most
Digital Delay devices which are capable of analog voltage control
actually step between delay values rather than continuously changing
value. This tends to cause zipper noise. In order to vary the
delay (or the pitch) continuously the sample rate clock must be
voltage controlled. While not impossible, this is quite difficult.
If you are sampling at 48 kHz which would give you a maximum input
frequency of around 20 kHz, and then you wanted to either decrease
the delay time or raise the pitch by two octaves, your sample rate
clock would now be running at 192 kHz. If you slow down below 48
kHz you will lose high end response or generate some truly nasty
artifacts, so the effective range is only about 2 octaves using
modern converters if you want to be continuously variable without
stepping.

It may be possible to get more range with a delta/sigma scheme or by
using a flash converter with a compander. This is something I'm
personally interested in exploring, as I'm interested in the musical
applications of delay lines, but I haven't had time to play around
with any kind of circuit design yet.

The frequency shifter is another animal entirely. The Encore
Electronics module is quite wonderful, but as someone else pointed
out a frequency shifter does not maintain the integer spacing of
harmonics present in the input signal, so it really does not shift
pitch.