Tremolo

Tremolo is a musical effect characterized by a rapid, regular variation in the loudness or pitch of a note or group of notes, producing a trembling or shimmering sound. The term comes from the Italian tremolo, rooted in tremere, to tremble. Historically, tremolo described a rapid repetition of a single note or a rapid alternation between two notes, notated with slashes or beams between notes.

On bowed strings, tremolo is achieved by rapidly moving the bow to create a pulsing effect. In keyboard music, tremolo can be indicated by repeated notes or by a rapid alternation between two notes. In organ playing, a tremulant is a mechanism that modulates the tone color and sometimes the loudness to create a shimmering effect. In modern electronics, tremolo commonly refers to amplitude modulation, a periodic variation in loudness produced by a low-frequency oscillator.

There are two main contemporary interpretations. Amplitude tremolo, the most widespread form in popular music and synthesis, modulates volume with adjustable rate and depth. Measured tremolo or tremolo between two notes involves rapid repetition of a written pitch or alternation between two pitches, and is often used in classical guitar notation or piano and keyboard writing.

Distinctions with vibrato are important: tremolo generally refers to amplitude modulation, while vibrato denotes pitch modulation. In practice, the word tremolo is sometimes used interchangeably with vibrato or misapplied to guitar hardware that produces pitch changes, contributing to occasional confusion in everyday usage.