Trills are more or less rapid and an unmeasured alteration between a main note and an upper auxiliary tone and semitone above. In the 16th century and early 17th century, trills optionally begun with its main note, or its upper auxiliary note, fulfill its melodic function.
When it has a harmonic function, it would begin on the upper auxiliary note, which was ‘a common practice’ in the late baroque era. When a trill is a cadential trills, it is particularly prominent that it has a harmonic function.
A trill must begin with its upper auxiliary note, it immediately proceeds the note to be trilled.
“All notes before a close is to be shaked, all shakes are taken from the note above”
Due to the appoggiatura like quality, the 1st note of an upper note trill is always and necessarily takes the beat, and always with some degree of stress. It is impossible to over emphasize the importance of stressing the top note of the trills not the bottom notes. The relationship between the trill and long appoggiatura is that a trill is quite frequently notated by an appoggiatura written as a small note. The speed and number of repercussion in a trill is variable and unmeasured.
In the early Baroque Music, a trill was often written out and occasionally as measure repercussions.
“You must not divide the (written out) trill exactly note-for-note, but only try to make it rapid”
Although the trills are marked as regular in the table of ornaments, in Francis Couperin’s first book, L’Art de toucher le clavecin, Paris, they should begin more slowly than they finish. The speed of regularity of a trill depends on taste and context. There is no need to make all trills have the same speed. In sad music, trills are played more slowly, but in happy pieces they are to be played quickly. For trills to be played beautifully perfectly, they must be played at a regular speed and kept to the same rapidity.
Half Trill (Pralltriller) consists of 2 repercussions ie four notes. The last note of the four is the main note and it is held on plain if time allows, more repercussion can take place but not so many to prevent the main note from sounding unclear at the end.
The half-trill like the full trill, is an on-the-beat ornament, starting with the accented upper auxiliary, and if time allows may be more or less be prolonged.
The four notes have a natural tendency due to lack of time to become three, thus the half-trill (Pralltriller) is turned into an inverted mordent (Schneller). This is still an on-the-beat ornament, but starting with the main note. Due to the speed it takes, there can be little accent and no prolongation.
At speed, it is often very difficult to bring half-trill (Palltriller) or even inverted mordent (Schneller) precisely on-the-beat. Continuous trills on long and very long notes are intended for colouring or sustaining the tone. It does not require them to start on the upper auxiliary note nor do they need to be accented or prolonged. There is no necessity for ending, although there may be a desirability.
Trills on successions of short note are for brilliancy only. They are to be played on-the-beat and begin on the upper auxiliary note with a very brief and rapid speed with no ending. They are also considered as half-trills taking almost the whole of the short note.
2. Tremelo and Vibrato
Trill is known in the Italian vocal ornament, especially in the early Baroque period as a tremolo-like pulsation on one note, with or without a gradual acceleration of the pulsation, if time allows, but never precisely measured.
A tremolo for an instrument, which may be notated as a wavy line, either measured or unmeasured, is sometimes treated as an ornament.
In Baroque treatises, vibrato is habitually described as an ornament. In practice, its function is an ornament.
In the Renaissance and early Baroque periods, it was common to have an inverted (upper) mordent alternating with an upper auxiliary tone or semitone. During the main part of the Baroque period, the mordent was a rapid and unmeasured alteration between a main note and a lower auxiliary note tone or semitone. This lost its popularity moving into the Baroque era, but was replaced by Pralltriller (half-trill) curtailed to a Schneller (inverted mordent).
The standard mordent is an on-the-beat ornament, starting on the main principle note with a slight accent, that consists of three repercussions. A Mordent can be most effective if played with the lightest touch.
The Turn is a circling around a main note by playing a upper and lower auxiliary note a tone or semitone away. It is an ornament that falls on-the-beat and when accented has a purpose of melodic and harmony function; however when unaccented, it serves as melodic function for in-between-beat.
The standard (upper) turn commences on the upper auxiliary note, passes through the principle note and falls on the lower auxiliary note and returns to the principle note. The inverted (lower) turn commences with the lower auxiliary, passes through the principle note, falls on the upper auxiliary note and returns to the principle note.
The standard (upper) and unaccented turns are more popular. Rhythms are mostly equal although a variety of unequal rhythms that may occur like triplets and dotted rhythms.