A synthesizer is an instrument that creates sound with electronic circuits or software and shapes its timbre. It is often shortened to synth. The keyboard-played form is the most familiar, but it also covers instruments driven by MIDI notes or a sequencer. Synths are used for a wide range of sounds, including bass, lead, pad, and effects.
The basic structure of sound creation
Most synthesizers create a source waveform with an oscillator, shape its frequency content with a filter, and set its level with an amp. An envelope then adds change over time, and an LFO or similar adds movement. Screens and names differ between models, but it is easier to understand if you look at them in terms of source, shaping, and change over time.
How it differs from a sampler
A synthesizer basically creates sound from waveforms and calculations, while a sampler plays back recorded audio. In practice there are synths that process samples and samplers that layer waveforms. Being aware of whether the sound starts from generation or from recording helps you sort out the difference.
Main synthesis methods
There are several approaches to making sound, including analog, virtual analog, FM, wavetable, additive, and physical modeling. You do not need to learn them all at once. Start by listening to how the oscillator, filter, and envelope change on a single software synth.
Playing it with MIDI
You can play a synthesizer from a MIDI keyboard or drive it with notes entered in the piano roll. The same MIDI data can sound completely different depending on the instrument or preset you choose. Being able to handle performance data and timbre separately is a major advantage of producing music on a computer.
Where to start when designing a sound
Choose a preset, set the register and level, then adjust only the parts you need. Rather than moving every knob from the start, changing the source waveform and the filter little by little makes the result easier to follow. The mechanics shared across instruments are covered in the software instrument article.
