Columbia subject headings:
Church music.
Music--500-1400--History and criticism.
Organ (Musical instrument)--History.
Harvard subject headings:
Church music--500-1400.
Music--500-1400--History and criticism
Musical instruments.
Organ (Musical instrument)--History
Princeton subject headings:
Church music.
Music--500-1400--History and criticism.
Organ (Musical instrument)--History.