Trumpets

I'm reading Sophie's World again, well not 'again' in the sense that i've ever actually finished the book in the past but more in the sense that i've started it a ton of times and haven't reached the end yet because -
a. I'm a slow reader, and
b. Philosophy, in my opinion, can only be read in small portions because you need time to reflect on what you have read so that your brain doesn't explode, and lets face it this book is thousands of years of philosophical thought compacted down into 400 pages so there is a lot to take in!
I'm about half way through, past socrates, descartes, aristole, plato, they've just given the very brief low down on Jesus and then Alberto Knox said something about the trumpets sounding and war cries and i realised that i'd never understood that before, when i read about trumpets in the Bible i think ... cool music - celebrations and worship, it never even crossed my mind to think 'trumpets sounding signalling troops going into battle, a way of telling everyone to attack' How strange that is, now he also points out that Jesus had a cool way of changing the meaning of these old fashioned phrases and perhaps thats something He did there but its still kinda weird that i didn't put two and two together. But anyway now i'm trying to think of situations were that phrase is used and maybe i didn't get the right meaning the first time round, like 'praise Him with the sounding of the trumpet, praise Him with harp and lyre' i figured that was just like ... play music and worship Him, but is it supposed to be 'go fight for His name'?

Any insights?