John Gill Commentary Nehemiah 11:23

"For there was a commandment from the king concerning them, and a settled provision for the singers, as every day required." — Nehemiah 11:23 (ASV)

For it was the king's commandment concerning them
Either of King David as some, see (Nehemiah 12:24) or rather of the king of Persia:

that a certain portion should be for the singers, due for every day ;
he settled a daily salary for them, to be paid out of his treasury; having perhaps a peculiar respect for such sort of men, being a lover of music, by means of which they had a settled habitation in Jerusalem.