Tremolo

Tremolos may be either measured, in which the exact rate of repetition or oscillation is specified, or unmeasured, in which it is not (the understanding being in that case that it should be performed as rapidly as possible).

Some electric guitars (in particular the Fender Stratocaster) use a lever branded a "tremolo arm"[3] or "whammy bar" that allows a performer to lower or (usually, to some extent) raise the pitch of a note or chord, an effect properly termed vibrato or "pitch bend".

[5] Although it had already been employed as early as 1617 by Biagio Marini and again in 1621 by Giovanni Battista Riccio,[6] the bowed tremolo was invented in 1624 by the early 17th-century composer Claudio Monteverdi,[7][8] and, written as repeated semiquavers (sixteenth notes), used for the stile concitato effects in Il combattimento di Tancredi e Clorinda.

[8] However, it was not till the time of Gluck that the real tremolo[clarification needed] became an accepted method of tone production.

[10] The undulating tremolo was produced through the fingers of the right hand alternately exerting and relaxing pressure upon the bow to create a "very uncertain–undulating effect ...

[8] There is some speculation that tremolo was employed in medieval Welsh harp music, as indicated in the transcription by Robert ap Huw.

In slower tempos (and/or meters with larger denominators), notes of shorter duration (corresponding to additional strokes) would be used.