Plug-in Reference

45
The included VST Instruments
About frequency modulation
Frequency modulation or FM means that the frequency of
one oscillator (called the carrier) is modulated by the fre-
quency of another oscillator (called the modulator).
• In Prologue, Osc 1 is the modulator, and Osc 2 and 3
are carriers.
Osc 2 could be said to be both carrier and modulator as if Freq Mod is
applied to Osc 2 it is modulated by Osc 3. If Osc 2 also uses frequency
modulation, Osc 3 will be modulated by both Osc 1 and Osc 2.
• The “pure” sound of frequency modulation is output
through the modulator oscillator(s).
This means that you should turn off the Osc 1 output when using fre-
quency modulation.
• The Freq Mod button switches frequency modulation on
or off.
• The Ratio parameter determines the amount of frequency
modulation.
Portamento
This parameter makes the pitch glide between the notes
you play. The parameter setting determines the time it
takes for the pitch to glide from one note to the next. Turn
the knob clockwise for longer glide time.
The “Mode” switch allows you to apply glide only when
you play a legato note (when switch is set to Legato). Le-
gato is when you play a note without releasing the previ-
ously played note. Note that Legato mode only works with
monophonic Parts.
Ring modulation
Ring modulators multiply two audio signals. The ring-mod-
ulated output contains added frequencies generated by
the sum of, and the difference between, the frequencies of
the two signals. In Prologue, Osc 1 is multiplied with Osc
2 to produce sum and difference frequencies. Ring modu-
lation is often used to create bell-like sounds.
• To hear the ring modulation, you should turn down the
output level for Osc 1 and 2, and turn up the “R.Mod” level
all the way.
• If Osc 1 and 2 are tuned to the same frequency, and no
modulation is applied to the Osc 2 pitch, nothing much
will happen.
If you change the pitch of Osc 2, however, drastic changes in timbre can
be heard. If the oscillators are tuned to a harmonic interval such as a fifth
or octave, the ring modulated output will sound harmonic, other intervals
will produce inharmonious, complex timbres.
• Oscillator Sync should be deactivated when using ring
modulation.
Noise Generator
A noise generator generates noise (all frequencies at
equal levels). Applications include simulating drum
sounds and breath sounds for wind instruments.
• To hear only the sound of the noise generator, you
should turn down the output level for the oscillators, and
turn up the Noise parameter.
• The Noise generator level is routed to Envelope 1 by
default.
See “Envelope page” on page 48 for a description of the Envelope
generators.