Psalms 81:1-3 - Joseph Benson’s Commentary on the Old and New Testaments

Sing aloud unto God our strength Our refuge and defence against all our enemies. Bring hither the timbrel, &c. All which instruments were then prescribed and used in their solemn meetings. Blow up the trumpet in the new-moon Which was a sacred and festival time. But this may be understood, either, 1st, Generally of every new-moon; or, rather, 2d, Specially of that new-moon which began the seventh month, the month Tisri, when a solemn feast was kept, which was always proclaimed by the sound of trumpets. Compare this passage with Leviticus 23:24, and Numbers 29:1, where this day is called a day of blowing of trumpets; it being the first day of the Jewish civil year, and the time when the world was supposed to have been created, the fruits being then ripe. “The fixing of the time of the new-moon among the Jews, for want of astronomical tables, was done in this manner. The first persons who observed, or thought they observed, the new-moon, were to repair immediately to the grand council to give notice of it. Inquiry was then made into the credibility of the informers, and whether their information agreed with such computations as they were then able to make. After which the president proclaimed the new-moon, by saying, מקדשׁ, mikdash, it is consecrated, or holy. This word was twice repeated aloud by the people, after which it was ordered to be proclaimed everywhere by the sound of the trumpet.” Univ. Hist., vol. 3. p. 33.