Our most recent group of songs originally grew out of some very fruitful conversations that I had with a pastor friend in Southern Michigan. Those conversations centered on the Messianic Psalms, particularly as regarding the Priesthood of Christ, and though I had already written a few songs based on a couple of the Messianic Psalms, many of these songs have grown directly from those conversations.
Indeed, we are not entirely done with this project, as I have begun working on a series of songs starting with Psalm 111 and culminating in Psalm 118 (also Messianic).
Once the passage has been chosen for a song, this is the methodology that I usually follow: translate and interpret the passage so as to understand the mind and heart of God through it, seek to understand the overall emotional tone and trajectory of the passage, write lyrics that expose the meaning and basic structure of the passage, and write the music. It is somewhat uncomfortable for me to describe this as a process, like there is some kind of mechanism or algorithm that can just churn out songs.
Nothing could be further from the truth.
The best way for me to communicate it is to view the process as a conversation with God that starts with His Word and that culminates in an expression that communicates, such as I am able, what He has taught me. Though most of my songs have followed this general trajectory and the mechanics described, I do not want you to get the idea that these songs are simply the result of a process or methodology. For me, there is a deep sense of conversation and worship that is intertwined with the whole process.
Writing these songs is a very much a part of my own personal growth in knowing and understanding God. That always begins with understanding His Word as much as is possible, saturating my mind and heart with the passage (and related scriptural concepts). So the process begins much as any sermon should, with prayer and a thorough understanding of the pasage under consideration - all as part of an ongoing relationship with God.
I find that translating from the original languages often illuminates certain properties of the passage in a way that is particularly helpful for building a song, though sometimes this is a considerable challenge (as with the Psalms). However, it is always fruitful. But it isn't enough to extract the data from the text; for our purposes we want to try and understand the emotional tone of the passage, either the emotion with which it is to be understood or the emotion that a right understanding should evoke.
To do this, I am looking for an overal emotional tone - for example: joyous, contemplative, agressive, or sorrowful. That will form an emotional core for the song's music. In addition to this, I am looking for an emotional trajectory, which will follow the trajectory of the content. Does the passage begin in doubt, working forward to confidence (like Psalm 77)? Maybe the passage expresses a subtext of external turmoil, while communicating the heart of one who trusts God (as in Psalm 16).
Music is uniquely suited to communicate these interpretive nuances, particularly with the Psalms, which were (of course) originally communicated with music. The words begin as a set of expressions that are essential to the passage, and then lyrics are finished with the goal of communicating the content of the passage in a way the exposes the meaning and tone of the passage in word, but that is only half of the song.
By the time the lyrics are being solidified, the emotional tone becomes more important, and I usually write emotional "cue words" along side of the lyrics (such as they are at that point). This is where the chord structure begins to form. I often pray and study with my guitar close at hand (I have a small Bible that fits in my guitar case). Sometimes I sing and worship the Lord with songs that remind me of the passage (or vice versa). Other times I just play and try to communicate the emotional content of those cue words. All the while working to find words that best express the meaning of the passage.
The music is usually comes together with the words, and by the time the lyrics are complete, the melody is nearly complete. From this point things progress somewhat more quickly. The whole process can take a month or even many months. Each song is the product of seeking to understand the mind of God in His Word, meditating on these things, and then seeking to respond in a way that is appropriate.
It is my prayer that these songs will open up and explain God's Word to the hearer, and that each will, by the understanding of God's Word, grow in their understanding of God, as He has revealed Himself. May the Lord grant that any vestiges of musical performance will be eclipsed by the wonder of His grace, through the gospel of Jesus Christ preached in music.