Simon And Garfunkel's The Sound Of Silence and Chubby Checker's 1960s dance hit The Twist are among 25 recordings selected for preservation at the Library of Congress in the US.
They are on the latest list of music from the 20th century being added to the National Recording Registry for long-term preservation for their cultural, artistic and historic importance.
The library said Checker's rendition of The Twist became a symbol of the energy and excitement of the early 60s after American Bandstand host Dick Clark chose Checker to record a new version of the song.
The 1966 album Sounds Of Silence by Paul Simon and Art Garfunkel was a hit in its day but not before the duo struggled and split early on. Their song The Sound Of Silence from the aftermath of President Kennedy's assassination had initially flopped - but it became a hit after it was re-edited as a single. That prompted the duo to reunite and quickly record another album under a similar title.
Garfunkel, 71, said he was thrilled and flattered to have his work preserved in the Library of Congress. He said the hit album was a life changer for him and Simon. "Da da dee, da dee, da dee," he sang in an interview.
"There's something fundamentally appealing about the simplicity of those lines," Garfunkel said.
"When you look at the little mesh, wire microphone ... and you address people on the other side of the mic, you hope that your performance will be special, and you hope that it will have lasting power," Garfunkel said. He said he remembers thinking in the 60s that "if we do really good and give a very special performance to these great Paul Simon songs, we might last right into the next century and be appreciated."
Their words and their tune have taken on special significance in American culture. Hearing Simon sing The Sound Of Silence on the 10th anniversary of the 9/11 attacks, NBC newsman Tom Brokaw briefly struggled for composure. This is the kind of impact the library was looking to preserve, "to celebrate the richness and variety of our audio heritage," said Librarian of Congress James Billington in announcing the selections.
The recording that received the highest number of public nominations for this year's registry was Pink Floyd's The Dark Side of the Moon. The library said it was notable as an example of "brilliant, innovative production in service of the music".
Other selections included the original 1949 cast album for South Pacific and the soundtrack to the popular 1977 movie Saturday Night Fever, starring John Travolta and featuring the Bee Gees, which revived the disco craze. The selections span from 1918 to 1980 and represent nearly every musical and recording category.