Therefore, the sound of the trumpet on Feast of Trumpets is a remembrance of the ultimate ingathering in the seventh month of God’s calendar. Remember Ephesians chapter 4 where it says this will not happen till we come together as a perfect man.
Who do you suppose that one man is in type? They came together in type in the seventh month as one man and they began to build. Seventh month is when the Feast of Trumpets begins to sound. Another reason given for the blowing of the trumpet on the Feast of Trumpets is for to remember the resurrection of the dead. Understand the words of
Isaiah 18:3 to be a prophecy directed to the dead. "As a banner is lifted on the mountains, you will see, and as a trumpet is sounded, you will hear." This was understood to mean that when the final trumpet will be blown, the dead would rise and see and hear again. One of the soon to come to pass events that we need to remember. The coming of Yeshua includes a great trumpet blast which wakes up those sleeping in the dust.
Ezra 3:1 366 1Cor 15:52
In his letter to the believers at Colossians, Paul states that all of the Biblical Festivals are "shadows of things to come, the substance of Christ."
[1] From the above list, it is obvious that the fall feasts are about the things to come. The list of remembrances reads like a synopsis of Jewish and Christian apocalyptic expectations in their proper order. The warning of impending judgment, the call to repentance, the fear of the Day of the LORD, the Ingathering of Israel, the rebuilding of the Temple, the final judgment, the resurrection of the dead and the coronation of the King are all familiar prophetic themes which both Jewish and Christian communities associate with the coming of Christ. It is clear that the Festival is ripe with end-times implications.
In view of Paul's statement that the festivals are "shadows of things to come," and in view of the ways in which the Spring Festivals of Unleavened Bread and Pentecost received a Messianic fulfillment within the events of the first coming of the Christ, Yeshua, one can hardly be surprised to find that the Fall Festivals speak to Christ's return. Yeshua himself invokes Feast of Trumpets imagery when he says, “They will see the Son of Man coming on the clouds of the sky with power and great glory. And He will send forth His angels with a great trumpet and they will gather together His elect from the four winds, from one end of the sky to the other.”
[2]
I lean more towards the seventh trumpet sounding long and hard throughout the last days from the Feast of Trumpets, through the Day of Atonement, and on through the Feast of Tabernacles right up to the eighth day.
For more trumpet references and purposes
Trumpets Used to Notify, Warn or Assemble Israel for War,
Numbers 10:2-9;
Jeremiah 4:19;
Amos 3:6;
Numbers 31:6;
Judges 3:27;
Judges 6:34, 7:822; I Samuel 13:3
Trumpets Used as a Sound of Peace, End of Strife II Samuel 2:28, 18:16, 20:22.
Trumpets Signified Crowning a King, or Revolt
II Samuel 15:10; II Samuel 20:1; I Kings 1:34, 39; II Kings 9:13; II Kings 11:12, 14
Trumpet Used in Temple Worship
II Chronicles 5:3, 12-14, 7:6;
Ezra 3:6, 10, 11; I Chronicles 15:24, 16:42
God's Voice is Full of Awesome Power, like a Trumpet
Revelation 1:10-11;
Revelation 4:1; Psalm 29
God's Trumpet-Like Voice at Mt. Sinai
Exodus 19:16, 19;
Exodus 20:18;
Hebrews 12:18-29
Trumpets and LORD's Judgment Day
Joel 2:1, 2, 11;
Zephaniah 1:6-7, 14-18; Psalm 98:6,9
Message of Day of Trumpets is that We Should Repent
Joel 2:1, 12-13,
Christ Comes to Rule Earth on the Last Trumpet Rev. 11:15, Trumpets, Atonement
Joel 2:15; Lev. 25:9
Now isn't that a FEAST of TRUMPETS for the children of God to feast upon?
[1] Colossians 2:16,17
[2] Matthew 24:30,31