I was thinking about this today whilst walking home from work and these two songs came on consecutively, and I was astonished that the former was actually longer than the latter.
Former: Red House Painters: 'Shadows' http://www.youtube.com/watch?v=e8TJuH4OkYU (6:07)
Latter: Titus Andronicus - Fear and Loathing in Mahwah, NJ http://www.youtube.com/watch?v=e8TJuH4OkYU (5:58)
There's not much difference really in song length (literally, a few seconds, but I've never, ever, thought of the Red House Painters song being 'an epic' whereas the Titus Andronicus song, for me at least, sound epic, with it's numerous parts and progression etc. Anyway, my point is that, is the length of the song what constitutes an epic for you? is it what the song contains? is it comparative to the rest of their songs (IE if some Mogwai songs were the closing tracks on other people's albums, they'd be epics, but for Mogwai, they're actually not really) or is it subjective entirely to you? For me, it used to be "well if it's over 6 minutes, then yes" but I'm wondering now...
I realise the thread for this is probably enough, but this caught my imagination.