Kommentar zu Schemot 19:19

הולך וחזק מאד WAXED LOUDER AND LOUDER — The manner of an ordinary person is that the longer he continues to blow a trumpet the sound he produces becomes weaker and fainter; but in this instance it went on getting stronger. And why was it thus (i. e. not so loud) at first? To make their ears receptive to as much as they were able to hear (Mekhilta d'Rabbi Yishmael 19:19:1).

MOSES SPOKE, AND G-D ANSWERED HIM BY A VOICE. In the Mechilta, the Rabbis have said²¹⁹Mechilta here. The language is that of Rashi. that this verse refers to the time of the Giving of the Torah, when Moses was proclaiming the commandments to Israel, as Rashi has written.
By way of the plain meaning of Scripture, the verse here does not yet speak of this. It is rather [to be explained as follows]: The Glorious Name²²⁰Deuteronomy 28:58. came down upon the mountain²²¹Verse 20. on the third day, and Moses brought forth the people out of the camp to meet the Glory which appeared to them, and they stood at the nether part of the mount.²²²Verse 17. Moses went up near to the head of the mountain, where the Glory was, in a place designated for himself, and he spoke with Israel, teaching them what to do. The Israelites heard the Voice of G-d answering Moses and commanding him, but they did not understand what He said to him. Thus He commanded Moses the precepts mentioned further on in this section: Go down, charge the people;²²³Verse 21. Go, get thee down, and thou shalt come up, thou, and Aaron with thee, etc.²²⁴Verse 24. This happened before the Giving of the Torah and also during the time when the Ten Commandments were given, for Moses did not go up to the top of the mount unto the thick darkness where G-d was²²⁵Further, 20:18. until after the Giving of the Torah. And so he said, “I stood between the Eternal and you at that time, to declare unto you the word of the Eternal; for you were afraid because of the fire, and went not up into the mount, saying²²⁶Deuteronomy 5:5. [that you will not ascend] as I did go up.” Some scholars²²⁷I have not been able to identify them. See my Hebrew commentary, p. 387, Note 5. explain that the Israelites were very much afraid of the voice of the horn which waxed louder and louder,²²⁸Verse 19 before us. and Moses would say to them at first: “Direct your thoughts, for now you will hear the Voice in such a manner,” and immediately G-d answered him by a voice.

משה ידבר והאלוקים יעננו בקול, Moses would speak and G'd answered him by voice. Moses may have uttered words of song and praise before G'd, much as someone who is received in an audience by a king praises the ruler who has granted him the audience. The קול with which G'd answered may have been the sound of the shofar mentioned in the next verse. This sound was an indication that G'd approved of what Moses told him. The word בקול means "in a loud voice," so that all the people could hear G'd speak with Moses and accept him as a true prophet. I believe that the Torah mentions this to tell us that Moses experienced a promotion when G'd answered him thus although G'd had also answered Moses previously. Our sages in the Mechilta understand the answer the Torah speaks of as the Ten Commandments which G'd was about to address to the people. They say that G'd increased the power of Moses' voice so that he could be heard by the whole nation. I believe that this is a homiletical approach to our verse.