Charles Ellicott Commentary Revelation 14:2

"And I heard a voice from heaven, as the voice of many waters, and as the voice of a great thunder: and the voice which I heard [was] as [the voice] of harpers harping with their harps:" — Revelation 14:2 (ASV)

And I heard a voice . . .—Translate, And I heard a voice out of the heaven. The saints stand with their Lord, the Lamb, on Mount Zion, and just as long ago a voice came from heaven bearing witness to Christ, so around the dwelling place of the saints heavenly voices are heard, full of majesty, tremendousness, and sweetness, as though the sounds of sea and thunder blended with the music of heavenly harps.

We call to mind the magnificent Psalm 29; there the saints, secure in Zion, hear all around them the voice of God in the thunder and in the sea, while in His safe sanctuary the saints can sing of His honour.