1 Chronicles 15:18

Their brethren of the second degree; the first rank or degree of sacred musicians being those three famous persons named 1 Chronicles 15:17, next unto whom were these here named. The porters; who were to keep the doors of the tabernacle and courts but withal were instructed in music and singing, that when they were free from attendance upon their proper office, they might not be idle nor unprofitable persons in God's house.