Albert Barnes on Revelation 14:2

And I heard a voice from heaven. Showing that the scene is laid in heaven, but that John in the vision was on the earth.

As the voice of many waters. As the sound of the ocean, or of a mighty cataract. That is, it was so loud that it could be heard from heaven to earth. No comparison could express this more sublimely than to say that it was like the roar of the ocean.

As the voice of a great thunder. As the loud sound of thunder.

And I heard the voice of harpers. In heaven: the song of redemption accompanied with strains of sweet instrumental music. For a description of the harp. Isa 5:12.

Harping with their harps. Playing on their harps. This image gives new beauty to the description. Though the sound was loud and swelling, so loud that it could be heard on the earth, yet it was not mere shouting, or merely a tumultuous cry. "It was like the sweetness of symphonious harps." The music of heaven, though elevated and joyous, is sweet and harmonious; and perhaps one of the best representations of heaven on earth is the effect produced on the soul by strains of sweet and solemn music.

(d) "voice" Rev 19:6 (e) "harping" Rev 5:8,9