The trill (or shake, as it was known from the 16th until the early 20th century) is a musical ornament consisting of a rapid alternation between two adjacent notes, usually a semitone or tone apart, which can be identified with the context of the trill (compare mordent and tremolo). It is sometimes referred to by the German Triller, the Italian trillo, the French trille or the Spanish trino. A cadential trill is a trill associated with each cadence. A trill provides rhythmic interest, melodic interest, and—through dissonance—harmonic interest. Sometimes it is expected that the trill will end with a turn (by sounding the note below rather than the note above the principal note, immediately before the last sounding of the principal note), or some other variation. Such variations are often marked with a few appoggiaturas following the note bearing the trill indication.
Notation
In most modern musical notation, a trill is generally indicated with the letters (or sometimes simply ) above the trilled note. This has sometimes been followed by a wavy line, and sometimes, in the baroque and early classical periods, the wavy line was used on its own. In those times the symbol was known as a chevron. The following two notations are equivalent:
Both the "" and the wavy line are necessary for clarity when the trill is expected to be applied to more than one note (or to tied notes). Also, when attached to a single notehead in one part that corresponds to smaller note values in another part, it leaves no room for doubt if both the letter and line are used.
The usual way of executing a trill, known as a diatonic trill, is to rapidly alternate between the written note and the one directly above it in the given scale (unless the trill symbol is modified by an accidental, understood to apply to the added note above; this is a chromatic trill).
Listen to an example of a short passage ending on a trill. The first time, the passage ends in a trill, and the second, it does not.
This is an alternative trill:
These examples are approximations of how trills may be executed. In many cases, the rate of the trill does not remain constant as indicated here, but starts slower and increases. Whether it is played this way or not is largely a matter of taste.
The number of alternations between the notes played in a trill can vary according to the length of the notated note. At slower tempos, a written note lasts longer, meaning more notes can be played in the trill applied to it; but at fast tempi and with a short note, a trill may be reduced to nothing more than the indicated note, the note above it, and the indicated note again, in which case it resembles an upper mordent.
Trills may also be started on the note above the notated note (the auxiliary note). Additionally, a trill is often ended by playing the note below the notated one, followed by the note itself.
In specific styles
In baroque music
Hugo Riemann described the trill as "the chief and most frequent" of all musical embellishments. In the baroque period, a number of signs indicating specific patterns with which a trill should be begun or ended were used. In the Klavierbüchlein für Wilhelm Friedemann Bach, Johann Sebastian Bach lists a number of these signs together with the correct way to interpret them. Unless one of these specific signs is indicated, the details of how to play the trill are up to the performer. In general, however, trills in this era are executed beginning on the auxiliary note, before the written note, often producing the effect of a harmonic suspension which resolves to the principal note. But, if the note preceding the ornamented note is itself one scale degree above the principal note, then the dissonant note has already been stated, and the trill typically starts on the principal note.
Several trill symbols and techniques common in the Baroque and early Classical era have fallen entirely out of use, including for instance the brief Pralltriller, represented by a very brief wavy line, referred to by Carl Philipp Emanuel Bach in his Essay on the True Art of Playing Keyboard Instruments (Versuch) (1753–1762).
Beyond the baroque era, specific signs for ornamentation are very rare. Continuing through the time of Mozart, the default expectations for the interpretation of trills continued to be similar to those of the baroque. In music after the time of Mozart, the trill usually begins on the principal note.