Commentaries:
The commentaries are about equally divided as to which festival or festivals are intended here. Is it speaking of the spring or the fall feasts? Passover and Tabernacles both fall on a full moon, and obviously, both are preceded on the first day of the month by a new moon. However, two things tend to throw the weight toward the fall festivals.
First, the superscription of the psalm is gittith. Gittith, though it is the term for a musical instrument, literally means "winepress." It is associated with the fall harvest of grapes because of its customary use by the vintners then.
Second, and more authoritative, is the word "trumpet." All the commentators duly report that this refers to the ram's horn. Instructions for the use of trumpets are given in Numbers 10, but it makes no distinction as to which trumpet (ram's horn or silver) should sound at the beginning of each month. However, Jewish tradition emphasizes that the silver horns were blown at the beginning of each month except Tishri 1, the Feast of Trumpets. The weight of evidence at this point inclines toward the feasts of Trumpets and Tabernacles.
Verse 4 explains that God established a law in Joseph as a testimony witnessing to a historical fact: his release from prison and elevation to prime minister. Thus, this psalm gives us the time setting for Joseph's experiences in Genesis 41: Tishri 1, which became the Feast of Trumpets! On this feast day, Joseph was removed from his hard labor, as Psalm 81:6 relates. The psalmist shows an encouraging parallel between God and Joseph. Both are saviors, and we can take encouragement from what happened to Joseph. God did not forget him!
John W. Ritenbaugh
God's Promises Are Sure!
Other Forerunner Commentary entries containing Psalms 81:6:
Psalm 81:1-6