Comment #25 on issue 2823 by lemzw...@gmail.com: Patch: Fixes position of mensural c clef
http://code.google.com/p/lilypond/issues/detail?id=2823
Here you can see the Vienna manuscript of Ockeghem's missa (starting on page 421). Note that it doesn't use the `double clefs'; instead, it explicitly writes out the voices.
http://aleph.onb.ac.at:80/F/P5BQHEXI8TY81I1386VUHPKUUA5GY3JG1NI3KCN7I8DV4Y3MQ4-08287?func=service&doc_library=ONB06&doc_number=000145564&line_number=0005&func_code=WEB-FULL&service_type=MEDIA;
