EFM1 Modulator and carrier controls in Logic Pro for iPad
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 FM intensity controls the level of these overtones.
At the core of the EFM1 synthesis system is a multiwave modulator oscillator and a sine wave carrier oscillator. The basic sine wave of the carrier oscillator is a pure, characterless tone.
To make things more sonically interesting, you use the modulator oscillator to modulate the frequency of the carrier oscillator. This modulation occurs in the audio range—you can hear it—and results in a number of new harmonics becoming audible.
The pure sine wave of the carrier oscillator is combined with the newly generated harmonics, making the sound more interesting.
Changes to the ratio of the two oscillators is achieved by adjusting the Harmonic parameters, found in both the Modulator and Carrier sections. Additional tuning control is provided by the Fine (tune) parameters.
Modulator parameters
Harmonic slider and field: Set the tuning ratio between the modulator and carrier oscillators. See Set the EFM1 tuning ratio.
Fine knob and field: Adjust the tuning between two adjacent harmonics, as determined by the Harmonic controls of both oscillators. The range of this control is ±0.5 harmonic. In the centered position, Fine tune does not have an effect. Double-tap to center the knob. Depending on the amount of detuning, you will hear one of the following:
A subtle “beating” of the timbre if lower detuning amounts are used.
New harmonic and inharmonic overtones if high detuning amounts are used.
Env to Mod Pitch knob and field: Determine the impact of the modulation envelope on the pitch of the modulator oscillator. See EFM1 modulation parameters.
If you turn the knob clockwise, you increase the effect of the modulation envelope. If you turn the knob counterclockwise, you invert the effect of the modulation envelope, as follows: the envelope slopes down during the attack phase and slopes up during the decay and release time phases.
If you double-tap to center the knob, the envelope has no effect on the pitch of the modulator oscillator.
Wave knob and field: Choose a different waveform for the modulator oscillator. See Choose an EFM1 modulator waveform.
Carrier parameters
Harmonic slider and field: Set the tuning ratio between the modulator and carrier oscillators. See Set the EFM1 tuning ratio.
Fine knob and field: Adjust the tuning between two adjacent harmonics, as determined by the Harmonic knobs of both oscillators. The range of this control is ±0.5 harmonic. In the center (0) position, Fine (tune) has no effect. Double-tap to center the knob. Depending on the amount of detuning, you will hear one of the following:
A subtle “beating” of the timbre if lower detuning amounts are used.
New harmonic and inharmonic overtones if high detuning amounts are used.
Fixed Freq button: Disconnect the carrier frequency from keyboard, pitch bend, and LFO modulations, resulting in a carrier tone that is free of these modulation sources.
FM Intensity knob and field: Set the amount of carrier oscillator frequency modulation by the modulator oscillator. Adjust to increase the intensity and number of overtones, making the sound brighter. Also see EFM1 MIDI controller assignments.Note: Although the technology behind it is very different, you could compare the FM Intensity parameter with the Filter Cutoff parameter of an analog synthesizer.
- Env to FM knob and field: Determine the impact of the modulation envelope on FM intensity. See EFM1 modulation parameters.
If you turn the knob clockwise, you increase the effect of the modulation envelope. If you turn the knob counterclockwise, you invert the effect of the modulation envelope, as follows: the envelope slopes down during the attack phase and slopes up during the decay and release time phases.
If you double-tap to center the Env to FM knob, the envelope has no effect on FM intensity.
Download this guide: PDF