I am ever so slightly fascinated by how pieces of pop music derive form classical. Some are obvious such as Beach Boys' Lady Linda. In some people don't believe me - Bee Gees (and Steps) Tragedy from Siegfried's Funeral March. In Which Decade, Mike drew my attention to Saint-Saens "Organ" Symphony/ If I Had Words - Scott Fitzgerald & Yvonne Keeley with the St. Thomas More School Choir.
Last week I put on a CD of Tchaikovsky's Serenade for Strings, which I've had for years, and immediately thought "That's Deacon Blue's Goodnight Jamsie"
I am currently listening to Penella's Il Gato montes and I hear Sylvia Vrethammar's Y Viva Espana. I suppose it's conceivable they both 'borrowed' a folk tune.