(MEI.shared) Groups non-text components that represent the content of the musical
text.
<music>Contains a single musical text of any kind, whether unitary or composite, for example,
an etude, opera, song cycle, symphony, or anthology of piano solos.
<music>Contains a single musical text of any kind, whether unitary or composite, for example,
an etude, opera, song cycle, symphony, or anthology of piano solos.