Reference for Rosh Hashanah 3:4
בַּתַּעֲנִיּוֹת, בְּשֶׁל זְכָרִים, כְּפוּפִין, וּפִיהֶן מְצֻפֶּה כֶסֶף, וּשְׁתֵּי חֲצוֹצְרוֹת בָּאֶמְצַע. שׁוֹפָר מְקַצֵּר וַחֲצוֹצְרוֹת מַאֲרִיכוֹת, שֶׁמִּצְוַת הַיּוֹם בַּחֲצוֹצְרוֹת:
(The shofroth) of fast days are of rams, bent, and their mouths covered with silver, and two trumpets in the middle. [There were two shofroth, one on each side, and trumpets in the middle.] The shofar (sound) was short, and the trumpets, drawn out; for the mitzvah of the day is with trumpets. [A fast day, generally, is for communal affliction, and it is written in that regard (Numbers 10:9): "… against the oppressor that oppresses you, then you shall sound the trumpets." And it is only in the Temple that this is done, but outside the Temple, when there is a shofar, there are no trumpets; and when there are trumpets, there is no shofar, it being written (Psalms 98:6): "With trumpets and the sound of the shofar, sound forth before the King, the L-rd" — "before the King, the Lord" (i.e., in the Temple), do so; not "before the King, the L-rd," do not do so.]