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)

171. There is no way to describe briefly how things look to angels in the heavens. To a considerable extent, they look like the things we see on earth, but they are more perfect in form and also more abundant.

We may conclude that there are things like this in the heavens because of what the prophets saw - for example what Ezekiel saw of the new temple and the new earth as described in chapters 40-48 [of his book], what Daniel describes in his chapters 7-12, what John saw as described from the first through the last chapter of Revelation, along with other visions presented in both the historical and the prophetic books of the Word. They saw things like this when heaven was opened to them, and heaven is said to be opened when our inner sight, the sight of our spirit, is opened. For the things that exist in heaven cannot be seen with our physical eyes, but only with the eyes of our spirit; and when it pleases the Lord, these are opened. At such times we are led out of the natural light that our physical senses are in and raised into the spiritual light in which we dwell because of our spirit. This is the light in which I have seen the things that exist in the heavens.