Columbia subject headings:
Harvard subject headings:
Folk songs, English--History and criticism.
Folk songs, Irish--History and criticism.
Gregorian chants--History and criticism.
Melodic analysis.
Troubadour songs--History and criticism.
Princeton subject headings:
Folk songs, English--History and criticism.
Folk songs, Irish--History and criticism.
Gregorian chants--History and criticism.
Melodic analysis.
Troubadour songs--History and criticism.