Vibrato is a periodic variation in the pitch of a note (its often confused with tremolo which affects only the volume). Violinists, guitarists and singers produce this effect with their fingers or voices, and perhaps for this reason the effect is not especially popular in pedal form. Of course, electronics can produce much more extreme vibrato than fingers. Even at more subtle settings though, the effect is generally simply on or off, whereas guitarists, like singers, usually add vibrato gradually and only towards the end of each note. In electronic form, this effect is perhaps best reserved for novelty use, especially where physical vibrato is not possible, for example on whole chords.