In Exodus 19:13; 20:18; Joshua 6:5, 20; 1 Samuel 13:3; Psalm 47:5; Isaiah 18:3; Matthew 6:2; Revelation 1:10; 8:2, trumpets signify celestial good, because the sounds of musical instruments correspond to affections for truth and good, and wind instruments to the latter. (Arcana Coelestia 8802)

The sounds of trumpets are heard in heaven when assemblies and appointments happen. So among the children of Israel, for whom everything was representative of heaven and the church, it was also commanded that they should make trumpets of silver, and that the sons of Aaron should blow them to call assemblies, when the camps set out on journeys, in days of celebration, in festivals, at the beginning of months, over burnt-offerings, for memorials, and going to war, as in Numbers 10:1-11. 'Seven trumpets' which the seven angels sounded in Revelation 16, signify the exploring and exposing the falsities and evils when people are in faith separate from charity. 'To sound a trumpet,' regarding its effect, signifies the revelation and manifestation of divine truth, and in the opposite sense, the deprivation of truth and desolation. 'Sounding with trumpets' signifies calling together on solemn occasions, and also exploring and discovering the quality of the church.

(Odkazy: Apocalypse Revealed 226)