See Read, p. 246-247. Whether the turn is accented or unaccented may be inferred from the timestamp — accented turns occur directly on the affected beat, unaccented ones do not.
<elementSpec rend="add" ident="turn" module="MEI.cmnOrnaments"><desc xml:lang="en">An ornament consisting of four notes — the upper neighbor of the written note, the
written
note, the lower neighbor, and the written note.</desc>
<classes>
<memberOf key="att.common"/>
<memberOf key="att.turn.log"/>
<memberOf key="att.turn.vis"/>
<memberOf key="model.ornamentLike.cmn"/>
</classes>
<content>
<empty/>
</content>
<constraintSpec ident="turn_start-type_attributes_required" scheme="schematron">
<constraint>
<sch:rule context="mei:turn">
<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>See Read, p. 246-247. Whether the turn is accented or unaccented may be inferred from
the
timestamp — accented turns occur directly on the affected beat, unaccented ones do
not.</p>
</remarks></elementSpec>