What technique is indicated by "tremolo"?

The technique called "tremolo" involves the rapid reiteration of the same note. This can create a shimmering or vibrating sound that adds intensity and dynamic interest to the music. Tremolo can be executed on various instruments, including strings, piano, and vocal performances, and it is often notated with specific symbols indicating the desired speed of the note repetition.

In contrast, the other options describe different techniques that are not aligned with the definition of tremolo. For instance, a slow and sustained sound corresponds more closely to a legato articulation. A gradual decrease in volume is identified as a "diminuendo" or "decrescendo," and an intense vibrato refers to a slight rapid pitch fluctuation, which is a separate technique altogether. Thus, the definition of tremolo distinctly matches the rapid reiteration of the same pitch.