Make for yourself two silver trumpets; you shall make them, beaten [from one block], and they shall be used by you to summon the congregation and to initiate the departure of the camps.

עשה לך שתי חצוצרות, “make yourself two trumpets, etc.” they were meant to be at Moses’ disposal at all times so that he would not have to send out to find someone who owned trumpets.

“Craft for you” – from your own. “Craft for you” – for yourself you craft, but not for another. You use them, but another does not use them. Know that Joshua, Moses’s disciple, did not use them, but rather shofars.... What is written there? “The people shouted, and they sounded the shofars” (Joshua 6:20) – it teaches that even his disciple Joshua did not use them.
life.

And the people shouted, and (the priests) blew with the trumpets; and it was when the people heard the sound of the trumpet, that the people shouted with a great shout, and the wall fell down in its place and the people went up into the city, every man opposite him, and they took the city.

Rabbi Yehoshua of Sikhnin [said] in the name of Rabbi Levi: The two trumpets that were [used] in the days of Moses were interred. One verse says: “They shall sound them…and they shall congregate to you” (Numbers 10:3), and one verse says: “Assemble to me all the elders of your tribe” (Deuteronomy 31:28); where were the trumpets? Say that they had already been interred in the days of Moses. The Holy One blessed be He said: Why should it be that he will die and his sons will be sounding the trumpets? No, because “there is no rule over the day of death.”

No man controls the will [of G-d's messenger] to retain the spirit, and there is no ruling on the day of death; neither is there discharge in war, nor will wickedness save the one who practices it.

“Craft for you” – you use them, as you are king, but no one else may use them other than King David, as it is stated: “The Levites stood [in their places]…and the song was sung, and the trumpets were sounded” (II Chronicles 29:26, 28). Rav said: The trumpets that were in the Temple were also sequestered, but King David would use a lute, as it is stated: “Awaken my honor. Awaken the harp and lute, I will awaken dawn” (Psalms 57:9). Rabbi Pinḥas HaKohen bar Ḥama said: A lute was suspended over David’s bed. When midnight would arrive, a north wind would blow on it and it would play on its own. Immediately, David and all the disciples who engaged in Torah study would rise, toil and drive sleep from their eyes, and study Torah until the rise of the morning star. That is why David would say: “Awaken my honor. Awaken the harp and lute, I will awaken dawn.” Typically, dawn awakens people, but I will awaken dawn, I awaken dawn.

Except for King David. We are forced to say that the intention is not David himself but the kings who descended from David, since the verse "And the Levites stood" which is cited is in 2 Chronicles 29, about King Hezekiah. And also regarding King Solomon it is written in 2 Chronicles 5 several times that there were trumpets...

And it played by itself. It seems to me according to what is said in Pirkei DeRabbi Eliezer (Ch. 31), from that ram that Abraham sacrificed instead of Isaac, not a single thing went to waste. Each part is accounted for including the sinews which were used for the harp of David, who would rise to serve HaKadosh Baruch Hu through this harp. And so, since the tendons were from the ram, which is an offering and forbidden to benefit from intentionally, it could only be benefited from without intention.

...And there is also another purpose, aside from arousal to focusing attention, that is realized through the sound of the trumpet; and that is that the sound of the trumpets removes all other worldly concerns from the heart of the listener, such that at that time he will only [direct] his heart to the matter of the sacrifice. But why should I go on so long? This is well-known to anyone who has ever bent his ear to hear, with focus, the trumpets or the sound of a shofar.

"Make for yourself two silver trumpets." "chatzotzros" (trumpets) means "chatzi tzuros" (half forms). As it is said, "upon the throne was a figure like the appearance of a man, above it" (Ezekiel 1:26). For man is only [the letters] dalet and mem (דל"ת מ"ם), and speech dwells within him. And when he cleaves to HaKadosh Baruch Hu, alufo shel olam (Master of the Universe), he becomes "adam" (אדם).

Even Joshua, his disciple, did not use trumpets because his understanding did not rise to that level. Rather, he used the shofar to symbolize the attribute of Justice which was poised against his enemies, for that was his attribute. This is also the attribute of David, who used the harp. And it is the blue dyed with the blood of the snail, which is the fish found in the Sea of Kinneret, for which this measure is called the harp of David, which played by itself. We find that each and every one uses the instrument that is appropriate for them according to their understanding, prophecy, and emotional qualities that they draw from, and this is clear.