Sigh is basically average. It is not bad, yet it brings nothing new to the genre, merely recycling what was already there. Inserting a trumpet changes nothing to the music itself, it merely provides novelty - it is noise that gets in the way between the listener and the music-in-terms-of-structure.
The tendency among metal bands to add new instruments (violins, opera vocals, flutes etc.) has turned out to be another chase after "something new" - in the superfluous, pop music meaning of the term - but without integrating it into the music itself, it is rubbish, and since it is not inserted because the instrument's musical qualities has anything to do with the music-as-structure in a meaningful way, it should be done away with. Get these hipsters out of metal.
Darkthrone provides an interesting counterexample: having reduced the music to the basic structure that gives meaning to it, they concentrate on the music itself rather than throwing all kinds of empty decoration at it so that it "sounds better" to the "average listener". The result: pure music, minimalist in nature, deceptively simple yet with a use of tremolo-based riff harmonies united to works worthy of (and eeriely reminding of) Johann Sebastian Bach.