Assertion: progressive rock | /r/CapableOf | shorten to progressive
Facets:
value: often
type: TEMPORAL
Source sentences:
text: Progressive rock (often shortened to "progressive", "prog rock" or "prog", also sometimes called, although not synonymous with, "art rock") is a form of rock music that evolved in the late 1960s and early 1970s as part of a "mostly British attempt to elevate rock music to new levels of artistic credibility".