Simplify the following text for a Grade 7 native English-speaking person.
Original: The idea of `` art rock '' has sometimes been used when talking about the `` progressive rock '' bands which became popular in the 1970s . Allmusic says that progressive rock and art rock are almost the same ; both used to describe rock music that is more artistic .
Simplified: However , in the 1970s , US rock music `` moved away from Art Rock '' , as southern rock bands became popular .