"...... all of the performances of the 20's and 30's and early 40's have largely disappeared from cultural relevance even though they were recorded.

But recordings from those decades are being listened to and incorporated into contemporary compositions by young musicians. Whether the mass market understands where music came from is irrelevant to the fact that old recordings coupled with 'the oral tradition' are the roots of new music.

Hawaiian chants mingled with California electronics, Caribbean rhythms... you get Jawaiian music.

Willie K, the Hawaiian Jimi Hendrix whose sets included opera, rock, traditional Hawaiian...

Paul Simon spent time researching African music. Ry Cooder, latin rhythms and themes.
Clapton and SO MANY others are students of Robert Johnson, an artist who only wrote a handful of songs. His singing, guitar playing and songwriting on his landmark 1936 and 1937 recordings have influenced later generations of musicians. Although his recording career spanned only seven months, he is recognized as a master of the blues, particularly the Delta blues style, and as one of the most influential musicians of the 20th century. The Rock and Roll Hall of Fame describes him as perhaps "the first ever rock star".

Maybe most people don't know the roots of the song theiy're streaming, but if they like a modern composition, it's most likely derivative of music that exists only on scratchy archived media that was heard by somebody and given new life.