Use ES2 frequency modulation in Logic Pro for iPad

The principle of frequency modulation (FM) synthesis was developed in the late 1960s and early 1970s by John Chowning. It was popularized by the Yamaha DX synthesizers in the 1980s. Although the ES2 can’t be compared with the DX series in the discipline of pure FM synthesis, it can achieve some of the signature sounds of these instruments.

In pure FM synthesis, the frequency of one signal generator, or oscillator, is altered (modulated) by another signal generator. Positive values from the second generator increase the frequency of the first generator. Negative values decrease the frequency. In a synthesizer, this type of modulation takes place in the audible range. Depending on the design of the instrument, you can hear the signals of either the first oscillator alone (being modulated by the other oscillator), or both oscillators. The interaction between the two generators alters the waveform signal of the first oscillator and introduces a number of new harmonics. This harmonic spectrum can then be used as the source signal for further sound processing, such as filtering, envelope control, and so on. See Frequency modulation (FM) synthesis for further information.

In ES2, the frequency of oscillator 1 (with a sine wave chosen—zero position for both the Waveform knob and Digiwave slider) can be modulated by the output signal of oscillator 2.

When oscillator 2 outputs a positive signal, the frequency of oscillator 1 increases.
When oscillator 2 outputs a negative signal, the frequency of oscillator 1 decreases.

The net effect of speeding up or slowing down the frequency of oscillator 1 in each waveform cycle is a distortion of the basic wave shape. This waveform distortion also has the side benefit of introducing a number of new, audible harmonics.

Important: The impact of any frequency modulations you perform depends on both the frequency ratio and the modulation intensity of the two oscillators.

The “pure” FM synthesis method uses a sine wave for both the first and second signal generator (both oscillator 1 and 2 would be limited to generating a sine wave in ES2 if you stuck with this approach). ES2, however, provides 100 Digiwaves and countless combinations of modulation intensities and frequency ratios that can be used for either oscillator. This provides a vast pool of harmonic spectra and tonal colors for you to experiment with.

Tip: The type of modulation that occurs can vary significantly when different waveforms are chosen for oscillator 2—the modulating oscillator—in particular.

Set the frequency ratio and adjust the modulation intensity

In Logic Pro ES2, adjust the frequency (Semitone and Detune) parameter values of one, or both, oscillators 1 and 2.
Set the FM amount (shown as a percentage) with the oscillator 1 Waveform knob.
This determines the intensity of frequency modulation.

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Logic Pro User Guide for iPad

Use ES2 frequency modulation in Logic Pro for iPad

Set the frequency ratio and adjust the modulation intensity