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Filling in the genre on mp3 songs on my phone. When I ripped the CDs, the genre was sometimes filled in from the database. Thing is some of what is defiantly R&R is tagged as Rock.
I don’t think there is a definitive answer but what is your opinion of the difference. I thought “Rock” began when things were tagged “Hard Rock”, “Punk Rock”, “Protest Rock”, etc.
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In our country it is used in about this way:
The "rock era" is from 1955 to the present.
The rock'n'roll period is the first years of the rock era. So about 1955-1960.