The interval between the main and auxiliary notes is usually understood to be diatonic unless altered by an accidental. The starting note of the trill; i.e., the written one or the ornamenting one, and the speed of alternation depends on performance practice. The starting point of the trill may be indicated by either a @startid, @tstamp, @tstamp.ges, or @tstamp.real attribute, while the ending point may be recorded by either a @dur, @dur.ges, @endid, or @tstamp2 attribute. It is a semantic error not to specify a starting point attribute.
<elementSpec rend="add" ident="trill" module="MEI.cmnOrnaments"><desc xml:lang="en">Rapid alternation of a note with another (usually at the interval of a second
above).</desc>
<classes>
<memberOf key="att.common"/>
<memberOf key="att.trill.ges"/>
<memberOf key="att.trill.log"/>
<memberOf key="att.trill.vis"/>
<memberOf key="model.ornamentLike.cmn"/>
</classes>
<content>
<empty/>
</content>
<constraintSpec ident="trill_start-type_attributes_required" scheme="schematron">
<constraint>
<sch:rule context="mei:trill">
<sch:assert test="@startid or @tstamp or @tstamp.ges or @tstamp.real">Must have one of the
attributes: startid, tstamp, tstamp.ges or tstamp.real.</sch:assert>
</sch:rule>
</constraint>
</constraintSpec>
<remarks xml:lang="en">
<p>The interval between the main and auxiliary notes is usually understood to be diatonic
unless altered by an accidental. The starting note of the trill;
<abbr>i.e.</abbr>, the written one or
the ornamenting one, and the speed of alternation depends on performance practice.
The
starting point of the trill may be indicated by either a <att>startid</att>,
<att>tstamp</att>, <att>tstamp.ges</att>, or <att>tstamp.real</att> attribute, while the
ending point may be recorded by either a <att>dur</att>, <att>dur.ges</att>,
<att>endid</att>, or <att>tstamp2</att> attribute. It is a semantic error not to specify a
starting point attribute.</p>
</remarks></elementSpec>