The point was that it should be extempore; if written down it ceased to be true descant, and was then called 'prick-song.'
Well said, wench; and the prick-song we use shall be our husbands.
This time they are speaking, not of descant, but of prick-song.
prick-song, music pricked or noted down, full of flourish and variety.
Any song which was printed in various parts was called a prick-song, to distinguish it from one sung extemporaneously or by ear.