Hello!, 
I'm very new here, so be kind!

Okay, so I want to write an essay on Heroic music and was wondering if you lot could help me. 
So what makes music heroic? I'm looking at specific elements of the music such as pitch, instrumentation, key, texture, time, and melody for example.
We all know get that sense of heroism when we listen to 'Nessun Dorma', but what Qualities of the music gives us this feeling? 
If you could maybe give me a fair few points on the subject and if anyone knows anything that I could get reading that would be great! thanks!

Michael