Sometimes the turn is not indicated at all, but it has nevertheless to be introduced if the shake is followed by an accented note (Ex. 20). If however the next following note is unaccented, no turn is required, but an extra principal note is added to the last couple of notes, that the trill may end as well as begin with the principal note (Ex. 21). When the trill is followed by a rest, a turn is generally made, though it is perhaps not necessary unless specially indicated (Ex. 22).
Mozart, 'Lison dormait,' Var. 8
Clementi, Sonata in G.
Beethoven, Trio, Op. 97
When a note ornamented by a shake is followed by another note of the same pitch, the lower subsidiary note only is added to the end of the shake, and the succeeding written note serves to complete the turn. This lower note is written sometimes as a small grace-note (Ex. 23), sometimes as an ordinary note (Ex. 24), and is sometimes
not written at all, but is nevertheless introduced in performance (Ex. 25).
Beethoven, Concerto in E♭
Clementi, Sonata in A.
Mozart, 'Salve tu, Domine.' Var. 4 (Cadenza).
Even when the trill-note is tied to the next following, this extra lower note is required, provided the second written note is short, and occurs on an accented beat (Ex. 26). If the second note is long, the two tied notes are considered as forming one long note, and the shake is therefore continued throughout the whole value.
Bach, Fugue No. 15, Vol. 2.
Very similar is the rendering of a shake on a dotted note:—the turn ends on the dot, which thus takes the place of the second of the two
notes of the same pitch. Thus the effect of the two modes of writing shown in Ex. 27 a and b, would be the same. If, however, the dotted note is followed by a note a degree lower, no turn is required (Ex. 28).
Handel, Suite 10. Allemande.
Rendering of both.
Handel, Suite 10. Allegro.
Trills on very short notes require no turn, but consist merely of a triplet—thus,
Mozart, 'Ein Weib.' Var. 6.
Besides the several modes of ending a shake, the commencement can also be varied by the addition of what is called the upper or lower prefix. The upper prefix is not met with in modern music, but occurs frequently in the works of Bach and Handel. Its sign is a tail turned upwards from the beginning of the ordinary trill mark, and its rendering is as follows—
Bach, Partita No. 1, Sarabande.
The lower prefix consists of a single lower subsidiary note prefixed to the first note of a shake which begins with the principal note, or of two notes, lower and principal, prefixed to the first note of a shake beginning with the upper note. It is indicated in various ways, by a single small grace-note (Ex. 31), by two (Ex. 32), or three grace-notes (Ex. 33), and in old music by a tail turned downwards from the commencement of the trill mark (Ex. 34), the rendering in all cases being that shown in Ex. 35.