Tremolo
In stringed instruments, the quick reiteration of the same tone, produced
by a rapid up-and-down movement of the bow. The string tremolo is
an important orchestral effect, widely used for dramatic passages or for
the purpose of orchestral coloring.
In singing, "tremolo" commonly means the excessive vibrato that leads
to deviation of pitch. The true vocal tremolo is an effect that is
practically never used today. In early music, however, it was one
of the most important ornaments.