לזכות
ר' צבי משה בן שרה לאה
רב משה צבי בן פרידה שמחה
חי' גיטל בת פייגע ביילא בלומא
Rosh Hashana is the "head" of the year. The head has three aspects to it: 1] It is the highest part of the body. 2] It encompasses and includes all of the body. 3] It leads the body.
Rosh Hashana has 3 parallel avodos: 1] The highest avoda of the year is תמליכוני עליכם - we crown Hashem as King. 2] Teshuva encompasses all of the mitzvos. 3] Rosh Hashana should inspire and lead us to do mitzvos the rest of the year.
The shofar as well parallels these three avodos: 1] With the blowing of the shofar we crown Hashem as King [as the gemara teaches]. 2] The shofar arouses us to teshuva [as the gemara teaches]. 3] The sounding of the shofar is a mitzva [besides its great spiritual symbolism].
As we alluded to, the shofar has two aspects: 1] It is a formal mitzva like other mitzvos. 2] It arouses us to teshuva. The Rambam mentions the fact that it arouses us to teshuva not in hilchos shofar but in hilchos teshuva. This is because in hilchos shofar the Rambam discusses teshuva as a mitzva and not as a trigger and inspiration for teshuva. So the correct location is hilchos teshuva. The Rambam doesn't even mention שתמליכוני עליכם because it is much too elevated to even be mentioned.
When we crown Hashem as King we go to a place of עצמות - Hashem Himself [kiviyachol] and that is where Hashem chooses us not because of any of our deeds but because we are [kiviyachol] one with Him. That is why we say the pasuk יבחר לנו את נחלתנו את גאון יעקב אשר אהב סלה - Hashem chooses for us our Land and chooses His people. By connecting to malchiyos we reveal the deepest connection that Hashem has to us as His chosen nation.
[Based on sichos given by the Lubavitcher Rebbe in 1963 - if you couldn't make it...]