11. It grew out of a composer's fascination with church polyphony and plainchant . 12. The text of a clausula differs from that of the plainchant melody underneath it. 13. It does not use the plainchant associated with the " Magnificat ". 14. Performances feature the original Bohemian plainchant tradition, including the earliest examples of polyphony. 15. They were inscribed in empty spaces in a manuscript that otherwise contains plainchants and texts. 16. He was quite an authority on plainchant . 17. Newly composed music on new texts was first introduced within the context of existing plainchant . 18. Of greater sophistication was the motet, which developed from the clausula genre of medieval plainchant . 19. The other plainchant repertories of the Christian West faced severe competition from the new Gregorian chant. 20. The principal example of this " unitonic order " tonality he saw in the Western plainchant . 