אִם־יִתָּקַ֤ע שׁוֹפָר֙ בְּעִ֔יר וְעָ֖ם לֹ֣א יֶחֱרָ֑דוּ אִם־תִּהְיֶ֤ה רָעָה֙ בְּעִ֔יר וַיהוָ֖ה לֹ֥א עָשָֽׂה׃
성읍에서 나팔을 불게 되고야 백성이 어찌 두려워하지 아니하겠으며 여호와의 시키심이 아니고야 재앙이 어찌 성읍에 임하겠느냐
Akeidat Yitzchak
The reason the Talmud discusses the exact nature of the teruah sound at great length, (Rosh Hashanah 32) is to show the importance attached to the value of external stimuli to achieve a certain frame of mind. Just as we are told in Kings II 3,15, that a certain frame of mind is necessary to achieve prophetic visions, -Elisha had to listen to music to achieve that frame of mind,- and just as we find David playing music when transporting the holy ark, (Samuel II 6,5) the frame of mind we are supposed to be in on Rosh Hashanah requires the sounds of a different instrument, i.e. the shofar. Since the prophet Amos proclaims "who does not tremble when the shofar is sounded?," we get the idea. (Amos 3,6) Blowing trumpets is not prescribed for this day. In fact, if someone manages to blow the shofar in such a manner that its sounds would be like real music, he has not fulfilled his duty. All this lends weight to the discussion in the Talmud about which is the right sound to be produced. Its is a wailing sound, kind of a sigh; the halachic decision is to arrange all the sounds in such an order as to insure that at some stage or other the correct sequence of tekiyah -teruah-tekiyah has been blown.