The alternative material in an ossia often provides a simpler, easier-to-perform option, while at other times the alternate material provides indications of performance practice, such as ornamentation. Often an ossia is rendered above the main staff on a reduced-size staff. Sometimes the alternate material occurs on the same staff as the primary text, but in a separate layer. In this case, the alternative material is often rendered in small-sized notation.
<elementSpec ident="ossia" module="MEI.cmn">
<desc xml:lang="en">Captures original notation and a differently notated version
<hi rend="bold">*present in
the source being transcribed*</hi>.</desc>
<classes>
<memberOf key="att.common"/>
<memberOf key="att.facsimile"/>
<memberOf key="att.ossia.log"/>
<memberOf key="att.ossia.vis"/>
<memberOf key="att.ossia.ges"/>
<memberOf key="att.ossia.anl"/>
<memberOf key="model.ossiaLike"/>
</classes>
<content>
<rng:choice>
<rng:interleave>
</rng:interleave>
<rng:interleave>
</rng:interleave>
</rng:choice>
</content>
<constraintSpec ident="Check_ossia" scheme="schematron">
<constraint>
<sch:pattern>
<sch:rule context="mei:measure/mei:ossia">
<sch:assert test="count(mei:*) = count(mei:staff)+count(mei:oStaff)">In a measure, ossia
may only contain staff and oStaff elements.</sch:assert>
</sch:rule>
<sch:rule context="mei:staff/mei:ossia">
<sch:assert test="count(mei:*) = count(mei:layer)+count(mei:oLayer)">In a staff, ossia
may only contain layer and oLayer elements.</sch:assert>
</sch:rule>
</sch:pattern>
</constraint>
</constraintSpec>
<remarks xml:lang="en">
<p>The alternative material in an ossia often provides a simpler, easier-to-perform option,
while at other times the alternate material provides indications of performance practice,
such as ornamentation. Often an ossia is rendered above the main staff on a reduced-size
staff. Sometimes the alternate material occurs on the same staff as the primary text,
but in
a separate layer. In this case, the alternative material is often rendered in small-sized
notation.</p>
</remarks>
</elementSpec>