The Greek verb aidō means to sing — specifically to sing in worship or celebration. It appears 5 times in the New Testament, in Ephesians 5:19, Colossians 3:16, and Revelation 5:9, 14:3 (twice). In the epistles, Paul commands believers to sing psalms, hymns, and spiritual songs to God. In Revelation, the redeemed sing a new song before the throne of God and the Lamb — a song no one else could learn.
Singing is the language of the redeemed heart. Paul connects aidō to being filled with the Spirit (Ephesians 5:18–19) and letting the word of Christ dwell richly (Colossians 3:16) — worship and the Word are inseparable. In Revelation, the new song (Revelation 5:9; 14:3) is the eschatological hymn of those purchased by the blood of the Lamb — the song of ultimate victory. The 144,000 could learn this song; no one else could (Revelation 14:3). Heaven is a singing place. The redeemed are a singing people. As Augustine wrote: He who sings prays twice.