Bitspeek versus vocoders, Example combinators – Sonic Charge Bitspeek RE User Manual

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Bitspeek Versus Vocoders

Vocoder is short for "voice encoder" and technically that means any device that is
capable of breaking down a voice signal into a set of parameters from which you
can reconstruct the voice intelligibly. With this terminology,

Bitspeek

may be called

an "LPC vocoder".

(LPC is short for "linear prediction coding"

However, in musical contexts, the vocoder we all know is a device consisting of a
filter bank that is controlled from a modulation source

(e.g. speech)

. This filter bank

is fed with an arbitrary carrier signal

(typically from a synthesizer)

that is played in-

dependently of the modulation source.

This is very different from how

Bitspeek

works. The formant filter in

Bitspeek

is not

implemented as a bank of bandpass filters. Instead, the analysis is divided into time
frames

(typically around 10ms each)

. For each frame the algorithm quickly con-

structs a resonant filter that closely represents the formants of the input speech.

In other words, whereas conventional vocoders works with a number of bandpass
filters at stationary frequencies,

Bitspeek

creates animated filters whose peaks are

precisely positioned in the spectrum. On the other hand, the signal is chopped up in
discrete time frames, whereas the conventional vocoder varies the formants
smoothly over time.

Example Combinators

Bitspeek

for Rack Extensions ships with some example Combinator patches. They

were created to be inspirational starting points for further exploration of the inter-
connectivity possibilities in Reason. Here is the run down with screenshots and ex-
planations.

ToyTalk (plain)

This is a plain single

Bitspeek

only, mainly provided as a reference point. It is config-

ured to produce a sound reminiscent of a certain early 80's toy.

SubSpeek

One

Bitspeek

controls the pitch

and the volume of a SubTractor,
which in turn is routed back into

Bitspeek

for filtering. In effect, the

SubTractor will replace the built-in
synth in

Bitspeek

, enabling com-

pletely new timbres.

Notice how we have connected
both

NOTE

and

PITCH CV OUT

achieve exact pitch tracking.

VOICE VOLUME OUT

to "Amp

Level" will make the SubTractor
play voiced sounds only

(and not

noise)