Bamidbar 18:23 The Levi[im] himself shall perform the service of the Tent of Meeting, and they shall bear their iniquity, an eternal decree for your generations; and among the Benei Yisrael they shall have no inheritance.

The Leviim are commanded that they alone are to perform certain services in the Temple, such as the closing of the gates, and the chanting during the offering of the sacrifices [offered on behalf of the whole community of Yisrael], for example: the daily Burnt-offerings, the various Additional Offerings, and the Peace-offerings of the community on the Festival of Shavuot.

This Mitzvah appears again in another form: "He [i.e. the Levi] shall minister in the name of HaShem his G-d, as all his brethren the Leviim do" (Devarim 18:7) on which the second chapter of Arakin says: "What is ministering in the name of HaShem? It means chanting." (Arakin 11a)

All the Leviim in Yisrael were thus divided into two groups – those that attended only to the gates of the Temple, and those that performed the chanting at the services. It was forbidden for a Leviim of one group to do the work generally assigned to one of the other group (Arakin 11b).

Much attention was devoted by Jewish law to the chanting of the Leviim in the Temple. The Levi whose voice had lost its vigor or its sweetness was disqualified for this service. While the actual chanting was the duty of the Leviim themselves, the accompaniment on musical instruments might be done also by Kohanim and dignitaries of Yisrael (Arakin 10a).

In the first and second Temples, musical instruments were a part of the daily worship–every day of the year, including Shabbat and holidays. The Mishnah even lists the number of instruments used in the Temple during specific holidays (Arakhin 2:3).

"There were never less than two trumpets, and their number could be increased without end; there were never less than nine lyres, and their number would be increased without end; but of cymbals there was but one, etc. There were never less than twelve Leviim standing on the Platform, and their number could be increased without end. None [of the Leviim] that were not of age could enter the Temple Court to take part in the service, save only when the Leviim stood up to sing; and they did not join in the singing with harp and lyre, but with the mouth alone, to add spice to the music" (ibid., 13b)

Following the recitation of the Song at the Sea, the Book of Exodus famously states that, “Miriam the prophetess, the sister of Aaron, took a tambourine in her hand; and all the women went out after her with tambourines, dancing.” (Exodus 15:20)

In addition to tambourines, the Book of Psalms lists a variety of instruments that can be used in praise of HaShem. One psalm encourages worshippers to “praise Him with the sound of the shofar!” (Psalms 150:1-4); another states that it is “good to praise the Lord” with a “ten-stringed harp, with voice and lyre together.” (Psalms 92:1-4)

Musical instruments are also an explicit part of the biblical commandments regarding holiday observance:  “And on your joyous occasions, your fixed festivals and new moon dates, you shall sound the trumpets… they shall be a reminder before your God.” (Numbers 10:10)

In the period of Bayit Sheini (second Temple), the Leviyim were best known as Meshorerim and Sho’arim – singers and gatekeepers. The Beit Hamikdash Levitical choir stood on the DUCHAN – the Levitical platform – located between Ezrat Yisrael – the Court of the Israelites and Ezrat Kohanim. The Mishna describes the DUCHAN, "R. Eliezer b. Jacob said, ‘Between the Ezrat Yisrael (Israel helpers) and the Ezrat Kohanim (Priest helpers) there was a step one Amah high and the Levitical platform was set thereon and on it were three steps each a half an Amah high; thus the Ezrat Kohanim were two and a half Amot higher than the Ezrat Yisrael." (Middot 2:6)

In the Bible, music is associated with praising God at times when words do not suffice. Musical instruments appear in this context in biblical narratives, poetry, and legal sections.

The Ramban further enlightens us – “The task of the Levities was not so much to protect the Mishkan [and Beit HaMikdash] as a militia, but rather to serve as an honor guard, as befits the royal palace” (1:53).

The Leviim’s duty in the Mishkan / Bait HaMikdash was to assist the Kohanim – among other ways by singing and playing musical instruments as sacrifices were brought.  Thus, music was an assumed part of worship in the biblical period.

When the Kohen poured the Nisuch Hayayin (wine libation) which accompanied the daily required morning and evening Tamid – into a silver cup embedded in the southwestern corner of the Mizbeach (altar), the Levi’im sang the psalm assigned for that day. Other Leviyim playing lutes, harps, lyres, flutes and a cymbal, accompanied the singers. The flutes were played only on special occasions.

Here is a brief description of what happened: "They gave him (the Kohein Gadol) the wine for the Nisuch Hayayin libation and the S’gan – the adjutant Kohein Gadol – stood beside him at the corner ‘horn’ of the Mizbei’ach with scarves in his hand and two Kohanim stood by the (marble) ‘table of the fat pieces’ with two silver trumpets in their hands. (This table was one of two located between the ascending-ramp south of the Mizbei’ach and the Bayit.) They blew a prolonged blast, a quivering blast and again a prolonged blast. Then they came and stood by Ben Arza (the choir master) – one at his right hand, one at his left. When the Kohein bent down to pour the Nisuch Hayayin, the S’gan waved the scarf as a signal, Ben Arza struck the cymbal and the Leviyim burst into song. When the Leviyim reached a break in the singing, they blew a prolonged blast on the trumpet and the people in the Azarah prostrated themselves. At every break they blew a prolonged blast and the people would prostrate themselves." (Tamid 7:3)

On Shabbat, the Leviyim sang but were unaccompanied by musical instruments. The vocal singing was considered an Avodah – an act of Temple service – and therefore was permissible on Shabbat; the instrumental accompaniment was not considered an Avodah and therefore was not permissible on Shabbat. (Sukkah 50a, 50b)

The Mishna (Tamid 7:4), recording the Shir Shel Yom  sung by the Leviyim in the Beit Hamikdash has long been incorporated into the Siddur and is recited during Musaf on Shabbat. Every day during the week the Leviyim sang the same psalm twice; once each during the Nisuch Hayayin, which accompanied the morning and afternoon Tamid.

What were the Shir Shel Yom: Shir Shel Yom (שִׁיר שֶׁל יוֹם), meaning "’song’ [i.e. Psalm] of [the] day [of the week]" consists of one psalm recited daily at the end of the Jewish morning prayer services known as shacharit. Each day of the week possesses a distinct psalm that is regerred to by its Hebrew name as the shir shel yom and each day’s shir shel yom is a different paragraph of Psalms.

Sunday: Psalm 24. Monday: Psalm 48. Tuesday: Psalm 82. Wednesday: Psalm 94, followed (in many communities) by the first three verses of Psalm 95. Thursday: Psalm 81. Friday: Psalm 93. Saturday: Psalm 92.

We have sung the Shir shel Yom for so many years in exile. Let us pray that the Temple will be rebuilt soon, and we will hear the sweet songs of the Levi’im once again.