The Everly Brothers were an American country-influenced rock and roll duo, known for steel-string acoustic guitar playing and close harmony singing. Isaac Donald "Don" Everly (born February 1, 1937) and Phillip "Phil" Everly (January 19, 1939 January 3, 2014) were elected to the Rock and Roll Hall of Fame in 1986 and the Country Music Hall of Fame in 2001.

Based on that paragraph can we conclude that this sentence is true?
The Everly Brothers never played music that was neither country nor rock and roll.
It's impossible to say