How can a synthesizer invent a sound no instrument makes?

A synthesizer can make a note swell like a cloud or buzz like an imaginary trumpet. In one common design, it begins with an oscillator: a circuit or calculation that produces a repeating electrical pattern. A speaker later turns the processed signal into moving air.

The oscillator’s repetition rate sets its basic pitch. Its waveform also matters. A smooth sine wave contains one frequency, while a repeating sawtooth contains a fundamental frequency and higher harmonics. Those added components help give the sound its distinctive color, called timbre.

A filter changes the balance of frequency components. A low-pass filter reduces higher-frequency components more than lower ones. Turning its cutoff control can make a rich buzzing signal sound darker or brighter without necessarily changing the note’s fundamental pitch.

An envelope controls how the level changes through a note. A quick attack starts sharply; a slow attack swells gradually. After a key is released, the release stage can let the sound fade rather than stop abruptly. The drawing contrasts two level envelopes applied to the same basic pitch.

These controls work together: a bright waveform with a gentle beginning feels different from the same waveform with an immediate strike. This is subtractive synthesis, named for shaping a rich sound partly by filtering components away. Other synthesizers combine waves, replay samples or model physical instruments. The keyboard can look familiar while the sound-making method opens an enormous space of possibilities.