Suppose you were tasked with identifying one definitive song from your list of favorite songwriter or songwriting team. First you’d really need to define what you mean by “definitive”.
A definition that appeals to me focuses on the song’s impact. How deeply did a song influence the culture? Did it change the very way we think about music? In the event of a tie, consider which song first comes to everyone’s mind when thinking of that songwriter or songwriting team.
Given this definition, some choices are easy. For Nirvana, it would be “Smells Like Teen Spirit”. For Irving Berlin, it would be “White Christmas”.
But other cases are trickier. What is Paul McCartney’s definitive song? Or Joni Mitchell, Rodgers and Hammerstein, Carole King, Robert and Richard Sherman, Taylor Swift, Bob Dylan or Ellie Greenwich?