What the Holy Spirit held back in chapter 7, by holding back ‘four winds’, is now released to unleash the full power of all the agencies of destruction the God intends.
The Lamb opened the seventh seal (v.1) and as a result there was silence in heaven for half an hour, so this is a very significant event. This seal has under it seven trumpets which seven angels, standing before God, sound off one after another (v.2).
Now what follows is the sounding of those seven trumpets (v.6). There is reference to the prayers of the saints (v.3,4), the true believers, so this indicates that the true church is still on earth, even under persecution (v.5). This is not some future post-rapture period as some teach.
Why a trumpet? The trumpet is used to give a signal. Usually it implied the start of the march or the charge of an army. See Joel 2:1,15, Jeremiah 4:5 and Ezekiel 33:1-6. Sometimes it calls the people to worship. See Numbers 31:6 and 1 Chronicles 15:24 .