I have done a simple Concordance search of the word 'sing' and 'song' in the New Testament, and I thought I would share the results with you. I hope these verses show us all that we are to sing together, sing often, and sing praises to God our Lord.
What if I don't feel like singing? Well, as Jesus taught us at the Last Supper, He was about to go to an excruciating and humiliating death, and have the world's sins laid upon Him, yet He led the disciples in the singing of a hymn (Matt. 26:30). Paul and Silas were in prison, and they sang (Acts 16:25). So it seems that singing is important for our emotional health, especially when we are under stress, as Jesus and Paul were.
But we are also to sing praises when we feel cheerful (James 5:13). We are to also sing God's praises in an assembly/congregation (Hebrews 2:12). How important is singing praises to our Lord God? The Apostle Paul answers this 1 Corinthians chapter 14. Paul recognized the wonderful spiritual gift from the Holy Spirit of speaking in tongues. But Paul recognized that singing hymns to God was more important than speaking in tongues because the Christian is using both their spirit and their mind when they sing (1 Cor. 14:15). While if someone is speaking in tongues only their spirit is praying, but their mind remains "unfruitful" (1 Cor. 14:14). So a beautiful part of singing praises to God is that you are using both your spirit and your mind in showing love to our Creator.
And finally, what sort of songs should we sing? Both Ephesians 5:18-:19 and Colossians 3:16, describe what Christians should sing as follows:
Let the word of Christ dwell in you richly, teaching and admonishing one another in all wisdom, singing psalms and hymns and spiritual songs, with thankfulness in your hearts to God. (Col. 3:16; see, Eph. 5:18-:19).
So Paul uses just about as broad of a description for the kind of songs Christians are to sing as there is: Old Testament psalms, hymns and spiritual songs. So if you love the old classic hymns – sing them! Open up your Bible, and sing a Psalm. If there is a catchy song you heard on Christian radio or in Church, sing it! But also notice what Paul connects to singing our Lord's praises – the word of Christ dwelling in us, and having a thankful heart. So take in God's Word, be grateful for the good things in your life, and sing praise to the Triune God. You'll be glad you did (that's my Amy Grant reference for today)!
Finally (really, this is my last point), I cannot leave the topic of singing without looking at the 'new song' described in Revelation. In Revelation chapter 5 we have a heavenly word picture painted for us, describing the 24 elders worshipping the Lamb of God. It describes this wonderful 'new song' as saying:
Worthy are you to take the scroll and to open its seals,
For you were slain, and by your blood you ransomed people for God from every tribe and language and people and nation,
And you have made them a kingdom and priests to our God, and they shall reign on earth. (Rev. 5:9-10; see, Rev. 14:3).
So what should we do? Sing praise to God in good times and in bad. Sing with thankfulness in our hearts. Sing and make music in your heart. Sing together. But most of all – just sing to the Sovereign Lord of the universe!