Vocoder - Waldorf Q Keyboard User Manual

Sound Parameters – Effects

Vocoder

The Vocoder effect is a special effect type. Only one Vocoder is allowed at a time. When you
have several sounds using a Vocoder, the one in the lowest Instrument slot wins. I.e., if you
have a sound with a Vocoder effect set up for Instrument 1 and another sound with a Vocoder
in Instrument 8, only the Vocoder in Instrument 1 works.
A Vocoder is a circuitry to process the frequency content of one signal with the frequency content of
another signal. This is done by splitting up the analysis signal (also known as Speech signal) with
bandpass filters into several frequency bands. The volume of each frequency band is then evaluated
with an envelope follower and the resulting envelope is used to control the volume of a bandpass
filter that processes the synthesis signal (also known as Carrier signal). The synthesis signal therefore is
filtered by as many bandpass filters as the analysis signal was so that each analysis filter finds its
synthesis filter counterpart.
This technique was already developed in World War II, but the plan was to use it to encrypt speech
when transmitted by radio, rather than using it to create musically useful sounds. However, this
shouldn't disturb you and you should feed a Vocoder with speech, drum loops or any other collection
of external audio material you like. The results will always be complex and interesting, sometimes
near to the original signal and sometimes far away. Experiment and have fun.
For the Vocoder, you always need two signals, a signal that is analyzed and another signal that is
used to be processed by the synthesis filters. The analyzed signal always comes from a different
source, either the external input or one of the internal routing busses. The synthesis signal is the
current sound, but if you like to use a different synthesis signal, set up the N/E Select parameter in
the Mixer Edit menu to feed the filters with e.g. the External In or one of the internal routing busses. It
might even be interesting if both the analysis and synthesis signal come from the same source,
especially when you set the synthesis band offsets to other values than +00. Then a low analysis band
might deliver the envelope for a high synthesis band and vice versa.
To restore the original signal as good as possible, the synthesis signal should only consist of a simple,
unfiltered noise that you generate with the Q's noise generator. For a spoken or sung voice, you
should add a sawtooth oscillator where the pitch determines the frequency of the speech. To get a
natural sounding spoken voice, you should modulate the pitch of this oscillator with a slow sine LFO
to simulate the emphasis.
Hint for working with the Vocoder
☞
Building a Vocoder setup
1. Connect the audio input of the Q with a 1/4-inch mono or stereo plug. In practice, a Y
cable is perfect for a stereo or dual mono signal input for the vocoder. Please be sure to use
a line signal. If you want to use a microphone be sure to use a pre amplifier to generate a
line signal.
2. With the Input Gain parameter in the Global menu you can increase the sensitivity. Please
refer to the chapter „Global Parameters" on page 143 for more details.
3. Select a sound program. We recommend the use of sustained pad or string sound.
4. Select the Vocoder as effect type for FX slot 1 or 2. Initialize the vocoder effect by holding
down the Shift button and pressing the corresponding FX Edit button.
Waldorf Q User's Manual 110