tremolo

noun

1. (countable, uncountable)A rapid repetition of the same note, or an alternation between two or more notes. It can also be intended to mean a rapid and repetitive variation in pitch for the duration of a note. It is notated by a strong diagonal bar across the note stem, or a detached bar for a set of notes (or stemless notes).

   “It commenced with a slow crescendo, so irresistibly lugubrious that two of our dogs at once raised their heads and swelled their voices into a responsive tremolo, which may have been heard and appreciated by their distant relatives.”

2. (countable, uncountable)A variation in the volume of a note or a chord, evoking a tremor or quiver.
3. (countable, uncountable)The device in an organ that produces a tremolo effect.