Erchin 2:5-6

Erchin (Arachin) 2:5

No fewer than six lambs verified as unblemished were kept in the Temple’s “chamber of lambs.” This was enough for the daily sacrifices of a Shabbos followed by the two days of yom tov of Rosh Hashana (which were observed even in Israel). This number could be increased with no upper limit. There were never fewer than two trumpets blown, nor nine lyres played, and their numbers could likewise be increased with no upper limit. There was, however, only one cymbal played.

Erchin (Arachin) 2:6

No fewer than 12 Levites stood on the platform while singing; this number could be increased with no upper limit. A minor Levite could only enter the Temple courtyard to serve while the Levites were singing. Minor Levites didn’t play the harp or the lyre, they only sang in order to add to the sweetness of the song. Rabbi Eliezer ben Yaakov says that the minor Levites don’t count among the requisite 12, nor do they stand on the platform. Rather, they stand on the ground with their heads between the feet of the adult Levites. These minors were called “the youth of the Levites.”