The front panel of most subtractive synthesizers provides similar signal-generating and processing modules—coupled with a number of modulation and control modules. The signal-generating and processing modules typically run from left to right, mirroring the synthesizer’s signal flow.
Signal-generating and processing components
Oscillators: Generate the basic signal. This is usually a waveform that is rich in harmonics (see Oscillators). Many synthesizers provide more than one oscillator, and almost all synthesizer oscillators can generate several waveform types.
Filter section: Used to alter the basic signal by filtering out (removing) portions of the frequency spectrum. Many synthesizers have a single filter that is applied universally to all oscillator signals. Multioscillator synthesizers can provide multiple filters, allowing each oscillator signal to be filtered in a different way (see Filters overview).
Amplifier section: Used to control the level of the signal over time. The amplifier has a module known as an envelope, which is divided into several elements that provide level control for the beginning, middle, and end portions of your sound. Simple synthesizers generally have a single envelope, which is used to control the oscillator (and filter) over time. More complex synthesizers can provide multiple envelopes (see Amplifier envelope overview).
Modulation and control components
Modulators: Used to modulate the signal-generating and processing components. Modulations can be machine-based—automatically generated by a synthesizer component—or can be manually activated by using the modulation wheel, for example. Most synthesizers have a component called an LFO (low frequency oscillator) to provide a waveform that modulates the signal. See Modulation overview.
Global controls: Set the overall characteristics of your synthesizer sound, such as glides between notes, pitch bends, and monophonic or polyphonic playback (see Global controls).