A trumpet symbolizes an ascent, the force of ascending. Only the priest has this force because he is in contact with the Creator. The Levites, on the other hand, only serve the priests. The part of our soul that belongs to the Creator is called a priest (Cohen). Levites, although they are the upper part that belongs to the Creator, they only engage in conducting the Light from Him to the lower. The priests work from the bottom up, for the Creator’s sake, while the Levites work from the top down, for the sake of the created beings.
The Torah, Numbers 10:9-10: If you go to war in your land against an adversary that oppresses you, you shall blow a teruah with the trumpets and be remembered before the Lord your God, and thus be saved from your enemies. On the days of your rejoicing, on your festivals and on your new-moon celebrations, you shall blow on the trumpets for your ascent-offerings and your peace sacrifices, and it shall be a remembrance before your God; I am the Lord your God.
The trumpets are used in order to raise the intention, why and where you are headed, and what you connect to. It is because these are not just ordinary trumpets that play a march, but vessels that make special sounds in special frequencies and in a special order and sequence, repeating them over and over again. All this symbolizes the phases of the correction of the vessel and the parts of the soul that are corrected in this specific manner. It is the most complex part of the wisdom of Kabbalah. Blowing the Shofar (Horn) in our world means simply to make some sounds, while it is a very serious action in a person’s internal work.
From KabTV’s “Secrets of the Eternal Book” 2/11/15