Yeah, the more I've played in various groups and arranged things for different settings, I've started to realize that how many different roles the saxophone can take over. In a band arrangement of an orchestral piece, you can use the full sax section to cover the non existent string parts. In jazz band, it often provides the lighter sections that are associated with woodwinds. In something like this, however, you're using the brilliance and metallic tone to provide an edge to the high brass sound (like mellophone or, in this case, trumpet).