Use Ultrabeat oscillator 1 FM mode in MainStage

FM (frequency modulation) synthesis is well suited for creating bell-like digital tones and metallic sounds. The principle of frequency modulation (FM) synthesis was developed in the late 1960s and early 1970s by John Chowning. It was popularized by Yamaha DX synthesizers in the 1980s. Although Ultrabeat 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.

In FM synthesis mode, oscillator 1 (the carrier) generates a sine wave. The frequency of the oscillator 1 sine wave is modulated by the waveform of oscillator 2 (the modulator).

• When oscillator 2 outputs a positive (or higher) frequency signal, the frequency of oscillator 1 increases.

• When oscillator 2 outputs a negative (or lower) frequency 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 introduces a number of new, audible, harmonics. The more complex the oscillator 2 waveform, the more partials are created by increasing FM Amount. Watch the display to see how the sine wave takes on an increasingly complex shape.