“Rejoice in the Lord, O ye righteous: for praise is comely for the upright. Praise the Lord with harp: sing unto him with the psaltery and an instrument of ten strings. Sing unto him a new song; play skilfully with a loud noise.” Psalm 33:1-3
It is right to praise the Lord, especially to do it with new songs, He loves it. In another version verse 3 says, “Compose new songs of praise to him, accompanied skillfully on the harp; sing joyfully.” He loves whatever is just and good but He’s tired sometimes of the same old songs that we sing, and worse most of them ain’t now sung coming from the heart. David is now suggesting we come up with new songs, for “the earth is full of the goodness of the Lord.” (Psalm 33:5).
What should we sing about?
Anything comely for the upright, anything right and just, and anything to extol his virtues – Psalm 33:5 says, “He loveth righteousness and judgment.” So many reasons why we sing but the greatest is to “Let all the earth fear the Lord : let all the inhabitants of the world stand in awe of him.” (Psalm 33:8). It is through our singing that “The Lord bringeth the counsel…” (Psalm 33:10).
The Lord gazes down upon mankind from heaven where he lives to see if any would come up with a new song for him. Don’t get me wrong, there is nothing wrong with our old classics, traditional songs, and some contemporary, for praise is comely but the point is new wine shouldn’t dry up. Psalm 98:1 says, “O sing unto the Lord a new song; for he hath done marvellous things: his right hand, and his holy arm, hath gotten him the victory.” In Revelations, whatever is sung is a new song, and is meant to celebrate a new victory.
Psalm 149 says,
 Praise ye the Lord . Sing unto the Lord a new song, and his praise in the congregation of saints.  Let Israel rejoice in him that made him: let the children of Zion be joyful in their King.  Let them praise his name in the dance: let them sing praises unto him with the timbrel and harp.  For the Lord taketh pleasure in his people: he will beautify the meek with salvation.  Let the saints be joyful in glory: let them sing aloud upon their beds.  Let the high praises of God be in their mouth, and a twoedged sword in their hand;  To execute vengeance upon the heathen, and punishments upon the people;  To bind their kings with chains, and their nobles with fetters of iron;  To execute upon them the judgment written: this honour have all his saints. Praise ye the Lord.
It worries God how there are no high praises of God from our lips.
“Finally, brethren, whatsoever things are true, whatsoever things are honest, whatsoever things are just, whatsoever things are pure, whatsoever things are lovely, whatsoever things are of good report; if there be any virtue, and if there be any praise, think on these things.” Philippians 4:8