Tremolo

In music, tremolo (Italian pronunciation: [ˈtrɛːmolo]), or tremolando ([tremoˈlando]), is a trembling effect. There are multiple types of tremolo: a rapid repetition of a note, an alternation between two different notes, or a variation in volume. 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).