Tremolo is also a short name for Tremolo bridge, a part of an electric guitar that can be used to create a vibrato pitch-variation effect. In the electric guitar terms, vibrato often refers to a rapid repetetive increase and decrease in volume, similar to the first meaning of tremolo as defined above. This opposite nameing of vibrato and tremolo was made popular by the products of the Fender Musical Instrument Corporation and has since become the norm in the nomenclature of players of electric guitar.
Tremolo is the rapid repetition of one note in music or a rapid alternation between two or more notes. It is sometimes called tremolando, especially when referring to a rapid repition on a bowed string instrument, one of the most commonly seen uses of the technique. Tremolo on a violin or similar instrument is sometimes combined with playing sul ponticello (over the bridge of the instrument), which gives a thin and reedy effect, often perceived to be "ghostly."
Another common use of the technique on one note is in the playing of the mandolin. Once a mandolin string is plucked, the note decays very rapidly, and by playing the same note many times very rapidly, the illusion of a sustained note can be created.
Tremolo on two or more notes is most frequently seen on the piano or other keyboard instruments. The composer Franz Liszt often calls for the technique to be used in his piano pieces. When used on the piano, tremolo can create a seemingly louder and larger sound, which can be sustained indefinitely. Historically, its use on keyboard instruments can be traced back to a time before the invention of the piano when harpsichords and similar instruments such as the spinet were standard. These instruments could not sustain notes for nearly as long as a modern piano, and so tremolo was used to simulate a longer sustain, as well as being used as an independent effect.
In music notation, tremolo is indicated by strokes through the stems of the notes (in the case of semibreves, which lack stems, the bars are drawn above or below the note, where the stem would be if there was one). Generally, there are three strokes, except on quavers (eighth notes) which take two, and semiquavers (sixteenth notes) which take one:
Because this is the same notation as would be used to indicate that regular repeated demisemiquavers (thirty-second notes) should be played, the word tremolo or the abbreivation trem., is sometimes added (particularly in slower music, when there is a real chance of confusion). Alternatively, more strokes can be used.
If the tremolo is between two or more notes, the bars are drawn between them: