10.6

Table Of Contents
354Logic Pro Instruments
Logic Pro Retro Synth FM oscillator
The synthesizer oscillators are used to generate the basic tonal color. This signal is then
sent to other parts of the synthesizer engine for shaping, processing, or manipulation. See
filter controls, amp and effect controls, modulation, and global and controller settings.
In FMsynthesis, the basic sound is generated by setting different tuning ratios between
the modulator and carrier oscillators and by altering the FMintensity. The tuning ratio
determines the basic overtone structure, and the FMcontrol sets the level of these
overtones.
At the core of the Retro Synth FM synthesis engine, you’ll find a multiwave modulator
oscillator—the (Wave) Shape slider, and a sine wave carrier oscillator—the FM (Amount)
slider. The basic sine wave of the carrier oscillator is a pure, characterless tone.
To make things more sonically interesting, the modulator oscillator is used to modulate
the frequency of the carrier oscillator. This modulation occurs in the audio range (you
can actually hear it), and results in a number of new harmonics becoming audible, thus
changing the tonal color.
The pure sine wave (of the carrier oscillator) is combined with the newly generated
harmonics, making the sound much more interesting.
You can make fine changes to the tuning ratio of the two oscillators (and therefore the
levels of the harmonics) by adjusting the Harmonic and Inharmonic controls.
FM synthesis is noted for synthetic brass, bell-like, electric piano, and spiky bass sounds.
FM oscillator parameters
Vibrato knob: Rotate to set the amount of vibrato (pitch modulation).
Modulation knob: Choose a modulation source (LFO or Filter Envelope), and set the
modulation intensity. This modulates the target chosen with the FM/Harmonic switch.
FM (Amount) slider: The carrier waveform is a simple sine wave. Drag to adjust the level
of this basic tone.
FM/Harmonic target switch: Choose a modulation target—FM (Amount), Harmonic, or
both—for the LFO or Filter Envelope.
The left switch position lets you use the LFO or Filter Envelope to modulate the FM
(Amount).