or indicated by certain signs.
The following are the embellishments most commonly found: Trill (or
shake), mordent, inverted mordent (or prall trill), turn (gruppetto),
inverted turn, appoggiatura and acciaccatura.

Usage varies greatly in the interpretation of the signs representing
these embellishments and it is impossible to give examples of all the
different forms. The following definitions represent therefore only the
most commonly found examples and the most generally accepted
interpretations.

65. The _trill (or shake_) consists of the rapid alternation of two
tones to the full value of the printed note. The lower of these two
tones is represented by the printed note, while the upper one is the
next higher tone in the diatonic scale of the key in which the
composition is written. The interval between the two tones may therefore
be either a half-step or a whole-step.

Whether the trill is to begin with the principal tone
(represented by the printed note) or with the one above is a
matter of some dispute among theorists and performers, but it
may safely be said that the majority of modern writers on the
subject would have it begin on the principal tone rather than
on the tone above. Fig. 40.

When the principal note is preceded by a small note on the
degree above, it is of course understood that the trill begins
on the tone above. Fig. 41.

The trill is indicated by the sign [trill symbol].

[Illustration: Fig. 40.]

[Illustration: Fig. 41.]

The above examples would be termed _perfect trills_ because they close
with a turn. By inference, an _imperfect trill_ is one closing without a
turn.

66. The _mordent_ [mordent symbol] consists of three tones; first the
one represented by the printed note; second the one next below it in the
diatonic scale; third the one represented by the printed note again.

[Illustration: Fig. 42.]

67. The _double (or long) mordent_ has five tones (sometimes seven)
instead of three, the first two of the three tones of the regular
mordent being repeated once or more. (See Fig. 43.)

In the case of both mordent and double-mordent the tones are sounded as
quickly as possible, the time taken by the embellishment being
subtracted from the value of the principal note as printed.

[Illustration: Fig. 43.]

68. The _inverted mordent_ [inverted mordent symbol] (note the absence
of the vertical line) is like the mordent except that th