The bible exhorts us to “guard our hearts” because they affect everything we do. Paul tells us to “put our hearts into” every work we do, no matter what it is. Jesus made it clear that the first and most 
important commandment was love. But he added that we should “love with all our hearts.” The best way to express our love for God is through worship. Music is a key means in which we can express our love for God with all our hearts. Since our hearts represent the seat of our emotions (among other things), it’s something we can let move us. Well, we should let it move us. Love and music have been handmaids forever. The longest song in the Bible, The Song of Solomon, is actually a love song.
To sing to God, to express our love to God in music, we have to put our hearts in it! Music isn’t just a set of sounds. It’s not even simply a set of pleasant sounds with harmony and tempo and all the other features that create what’s essential for any good song. It’s music with a message that moves me. A good piece of music gets inside of you. Kenton Anderson writes, “Evangelicals have a history of suspicion about the physical impact of music. Yet God created music, and he created us. The way that music affects the human body is one of God’s gifts to us. Like any gift, however, it must be used in ways that promote his glory. Instrumental music, or music without words, can produce the same affective result, but when words and music combine, the song truly moves the soul. Truthful lyrics and powerful music can have a healthy effect on each other. The cognitive impact of the words keeps the body’s physical response to the music focused and in line, just as the affective impact of the music keeps the head’s contemplation of the words from being dry and antiseptic.”
Nothing is more boring that to hear someone sing who doesn’t put their heart into it. You don’t need a good voice to express your love for God “with all your heart.” You just need to “let your light shine.” In my genre of music alone you’ll recognize people with terrible voices, yet have made millions of dollars as singers. In my opinion, no one had a worse voice than Bob Dillon! Even worse to me was the sound of Mick Jagger of the Rolling Stones. Janis Joplin won the heart of many young Americans with one of the worse female voices ever. But what made them famous was they put their hearts into it. No one could deny that! If you’ve ever seen footage of Janice you’d know exactly what I mean. Yet, with all her enthusiasm, the “get it while you can” theme of her life had a tragic ending. For the believer, there is a song with a happy ending, a song of salvation and eternal life.
Chuck
“Sing aloud, O daughter of Zion; shout, O Israel! Rejoice and exult with all your heart, O daughter of Jerusalem!” Zephaniah 3:14