John Wesley on Revelation 4:9-10

And when the living creatures give glory - the elders fall down - That is, as often as the living creatures give glory, immediately the elders fall down. The expression implies, that they did so at the same instant, and that they both did this frequently. The living creatures do not say directly, "Holy, holy, holy art thou;" but only bend a little, out of deep reverence, and say, "Holy, holy, holy is the Lord." But the elders, when they are fallen down, may say, "Worthy art thou, O Lord our God."