"I saw that the testimony of the True Witness has not been half heeded. The solemn testimony upon which the destiny of the church hangs has been lightly esteemed, if not entirely disregarded. This testimony must work deep repentance; all who truly receive it will obey it and be purified. EW 270.3"
"As many as I love, I rebuke and chasten: be zealous therefore, and repent."
The EGW passage directly references the message of the True Witness (Christ) and connects it to repentance and purification, echoing the call to repentance and zeal in Revelation 3:19. The EGW passage amplifies the call to repentance found in Revelation.
"Said the angel, “List ye!” Soon I heard a voice like many musical instruments all sounding in perfect strains, sweet and harmonious. It surpassed any music I had ever heard, seeming to be full of mercy, compassion, and elevating, holy joy. It thrilled through my whole being. Said the angel, “Look ye!” My attention was then turned to the company I had seen, who were mightily shaken. I was shown those whom I had before seen weeping and praying in agony of spirit. The company of guardian angels around them had been doubled, and they were clothed with an armor from their head to their feet. They moved in exact order, like a company of soldiers. Their countenances expressed the severe conflict which they had endured, the agonizing struggle they had passed through. Yet their features, marked with severe internal anguish, now shone with the light and glory of heaven. They had obtained the victory, and it called forth from them the deepest gratitude and holy, sacred joy. EW 270.4"
"And I heard a voice from heaven, as the voice of many waters, and as the voice of a great thunder: and I heard the voice of harpers harping with their harps:"
Both passages describe hearing a voice from heaven that is musical and powerful. Revelation 14:2 speaks of harps, while EGW describes a sound like many musical instruments. The descriptions evoke a similar sense of awe and divine presence.