Assertion: progressive rock | /r/HasProperty | experimentation
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text: Other genres of rock began to emerge such as progressive rock (experimentation with other instruments other than guitar, bass and drums, popularized by Pink Floyd), folk rock (traditional acoustic rock songs with a blues undertone popularized by Bob Dylan and Janis Joplin) and heavy metal (a thick, heavy, and highly amplified genre of rock popularized by Black Sabbath).