Plug-in Reference

60
The included VST Instruments
Mystic (Cubase only)
The synthesis method used by Mystic is based on three
parallel comb filters with feedback. A comb filter is a filter
with a number of “notches” in its frequency response, with
the notch frequencies harmonically related to the fre-
quency of the fundamental (lowest) notch.
A typical example of comb filtering occurs if you are using
a flanger effect or a delay effect with very short delay time.
As you probably know, raising the feedback (the amount
of signal sent back into the delay or flanger) will cause a
resonating tone – this tone is basically what the Mystic
produces. As you will see, this astonishingly simple syn-
thesis method is capable of generating a wide range of
sounds, from gentle plucked-string tones to weird, non-
harmonic timbres.
The basic principle is the following:
• You start with an “impulse sound”, typically with a very
short decay.
The spectrum of the impulse sound will largely affect the tonal quality of
the final sound. To set up an impulse sound on the Mystic you use a
slightly simplified version of the synthesis found on the Spector synth.
• The impulse sound is fed into the three comb filters, in
parallel. Each of these has a feedback loop.
This means the output of each comb filter is fed back into the filter. This
will result in a resonating feedback tone.
• When the signal is fed back into the comb filter, it goes
via a separate, variable lowpass filter.
This filter corresponds to the damping of high frequencies in a physical
instrument – when set to a low cutoff frequency it will cause high har-
monics to decay faster than the lower harmonics (as when plucking a
string on a guitar, for example).
• The level of the feedback signal is governed by a feed-
back control.
This determines the decay of the feedback tone. Setting this to a nega-
tive value will simulate the traveling wave in a tube with one open end
and one closed end. The result is a more hollow, square wave-like sound,
pitched one octave lower.
• A detune control offsets the fundamental frequencies of
the three comb filters, for chorus-like sounds or drastic
special effects.
Finally you have access to the common synth parameters
– two LFOs, four envelopes and an effect section.
• By default, envelope 2 controls the level of the impulse
sound – this is where you set up the short impulse decay
when emulating string sounds etc.
Ö The signal flow of the Mystic synth is illustrated in the
section “Diagrams” on page 73.
Sound parameters
The Impulse Control section
This is where you set up the impulse sound – the sound
fed into the comb filters, serving as a starting point for the
sound. The Impulse Control has two basic waveforms that
are filtered through separate spectrum filters with adjust-
able base frequency; the output is an adjustable mix be-
tween the two waveform/spectrum filter signals.