Assertion: improvisation | /r/HasProperty | based on variation techniques
Facets:
value: often
type: TEMPORAL
Source sentences:
text: In the later 18th century, improvisation, often based on variation techniques but not excluding the strictly polyphonic procedures of canon and fugue, challenged the ingenuity of virtuoso-composers repeatedly in public improvisational contests, such as those that pitted Mozart against Muzio Clementi and Ludwig van Beethoven against Joseph Wölfl.