John Gill Commentary 1 Chronicles 23:5

"and four thousand were doorkeepers; and four thousand praised Jehovah with the instruments which I made, [said David], to praise therewith." — 1 Chronicles 23:5 (ASV)

Moreover four thousand were porters
At the east, north, and south gates of the temple, in their turns;

and four thousand praised the Lord with the instruments ;
were singers in the temple, which in all made up 38,000:

which I made, said David, to praise therewith ;
which instruments he devised and ordered to be made to praise the Lord with; see (2 Chronicles 29:26) (Nehemiah 12:36) .