A hard task. I do not know if any of these songs changed the world, but they all stopped me in my tracks when I first heard them...in no particular order

At Last by Etta James
Red Cross Store by Mississippi Fred MacDowell
Hello Earth by Kate Bush
A Case of You by Joni Mitchell
Seven Yellow Gypsies by Martin Carthy
Swarthfell Rocks by The Watersons
Matty Groves by Fairport Convention
Someone Like You by Adele
Aqualung by Jethro Tull
King Henry by Steeleye Span
Natural Woman by Aretha Franklin
Monster by Kanye West

   Well, I could go on but these come instantly to mind.