Name a tune that.............

[Elric68]

Only one track ? I guess the first that comes to my mind as the typical and ideal prog song is Firth Of Fifth, which is the 1st prog track I ever listened as far as I can remember, and still one of my favourites:

It's between 10 and 15 minutes long, depending on the versions, there's a long (and a bit sad) instrumental part (sadness is an element you can find often in prog music and that I love), very emotionnal, and there are a few rythm changes during the song, so it's THE prog track