1. Sources of information ; 2. Principles of mensural notation ; 3. Definitions and descriptions of tactus ; 4. Tactus and rhythm ; 5. Tactus and signs in fifteenth-century music theory ; 6. Tactus and signs in sixteenth-century music theory ; 7. Tactus and tempo ; 8. The songs of Dufay ; 9. The L'homme armé masses of Ockeghem, Busnoys and Josquin ; 10. The five- and six-voice motets of Josquin ; 11. The Choralis Constantinus of Isaac ; 12. The masses of Palestrina ; 13. The madrigals of Rore ; 14. Popular songs and dances