Trumpets were used on joyful occasions and at the wars. There were two trumpets made of silver which the priests used, and instructions were given as to blowing different sounds for calling the princes together, for summoning all the congregation, or as an alarm for war. At the dedication of the temple, Solomon had 120 priests sounding with trumpets.
The use of trumpets set forth the public proclamation of God’s rights in His people, whether in their direction or in their relationship with Him. At the giving of the law, there was a loud voice of the trumpet proceeding from the mount, exceeding loud, so that all the people trembled.
In the Roman army, when it was about to start, the trumpet sounded three times: At the first trumpet they pulled down their tents; at the second they put themselves in order; when the last trumpet sounded, they started. When the Lord Jesus comes to fetch His saints, it will be with the voice of the archangel and with the trump of God (1 Thess. 4:1616For the Lord himself shall descend from heaven with a shout, with the voice of the archangel, and with the trump of God: and the dead in Christ shall rise first: (1 Thessalonians 4:16)). The “last trump” will sound at the resurrection of the saints (1 Cor. 15:5252In a moment, in the twinkling of an eye, at the last trump: for the trumpet shall sound, and the dead shall be raised incorruptible, and we shall be changed. (1 Corinthians 15:52)).
Concise Bible Dictionary (adapted)