Erchin 2:3-4

Erchin (Arachin) 2:3

They never sound fewer than 21 blasts in the Temple, nor more than 48. They never play fewer than two harps, nor more than six; not fewer than two flutes nor more than 12. On 12 days in the year, the flute was played in front of the altar: when slaughtering the Passover offering, when slaughtering the make-up Passover offering, on the first day of Passover, on Shavuos and on all eight days of Succos. They didn’t play a bronze flute but rather a reed flute, which makes a more pleasant sound. They finished with only one flute because it makes for a more pleasant resolution.

Erchin (Arachin) 2:4

Rabbi Meir says that the flutes were played by the servants of the kohanim but Rabbi Yosi says the flute players were of families from Beis Hapegarim and Beis Tziporiah, and from Emmaus, who married kohanim. Rabbi Chanina ben Antigonos says that the flute players were Levites.