Plug-in Reference

190
The Included VST Instruments
Prologue
About Frequency Modulation
Frequency modulation or FM means that the frequency of one oscillator (called the
carrier) is modulated by the frequency 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 is
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 frequency
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). Legato is when you play a note without releasing the
previously played note. Note that Legato mode only works with monophonic parts.
Ring Modulation
Ring modulators multiply two audio signals. The ring-modulated 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 modulation is often used to create bell-like
sounds.
• To hear the ring modulation, turn down the output level for Osc 1 and 2, and turn
up the “R.Mod” level all the way.
Sync button
(On/Off)
When Sync is activated, Osc 3 is slaved to Osc 1. This means that
every time Osc 1 completes its cycle, Osc 3 is forced to reset (start
its cycle from the beginning). This produces a characteristic sound,
suitable for lead playing. Osc 1 determines the pitch, and varying the
pitch of Osc 3 produces changes in timbre. For classic sync sounds,
try modulating the pitch of Osc 3 with an envelope or an LFO. The
Osc 3 pitch should also be set higher than the pitch of Osc 1.
Tracking button
(On/Off)
When Tracking is activated, the oscillator pitch tracks the notes
played on the keyboard. If Tracking is deactivated, the oscillator pitch
remains constant, regardless of what note is played.
Freq Mod button
(On/Off)
This switches frequency modulation on or off.
Wave Mod button
(On/Off)
This switches wave modulation on or off.
Waveform pop-up
menu (see
“Selecting
Waveforms” on
page 187)
Sets the basic waveform for the oscillator.
Parameter Description