A.T. Robertson Commentary Revelation 19:6

"And I heard as it were the voice of a great multitude, and as the voice of many waters, and as the voice of mighty thunders, saying, Hallelujah: for the Lord our God, the Almighty, reigneth." — Revelation 19:6 (ASV)

As it were the voice (ως φωνην). Used here three times, as once in verse 1: once of a second great multitude (οχλου πολλου), not of angels as in verse 1, but the innumerable multitude of the redeemed of 7:9; then "of many waters" (υδατων πολλων) as in 1:15; 14:2 like "the roar of a cataract" (Swete); and once more "the voice of mighty thunders" (βροντων ισχυρων) as in 6:1; 10:3f..

Saying (λεγοντων). The best attested reading, genitive plural of λεγω, agreeing with οχλου (genitive singular), for roll of the waters and the roar of the thunders were not articulate. Some MSS. have λεγοντες (nominative plural) referring also to οχλου, though nominative instead of genitive. The fourth "Hallelujah" comes from this vast multitude.

The Lord our God, the Almighty (Κυριοσ, ο θεοσ, ο παντοκρατωρ). For this designation of God see also 1:8; 4:8; 11:17; 15:3; 16:7,14; 19:15; 21:22. Cf. deus et dominus noster used of the Roman emperor.

Reigneth (εβασιλευσεν). First aorist active of βασιλευω. Probably ingressive prophetic aorist, "God became king" in fulness of power on earth with the fall of the world power.