As I start to think about how the individual tracks will sound, I am thinking about the emotion and the mood that I want to convey. The harmony of the song and the lyric are inextricable, they cannot be separated. They work together to form the meaning of the song.
For the most part, the harmony, melody, rhythm of the song will support the lyric. If it doesn't it forms a disbelief in the listener. We have to be careful that our music and words are saying the same thing. For example, if we sing a song about being Happy, but we fall behind the best slightly, the song will feel like it drags and the whole package will not be communicating "happy".
There are times when we may diverge on purpose and the music and the lyric become opposed, on purpose. This introduces a sense of sarcasm to the song. A few years ago, I wrote a song about technology and how it is spreading into every area of life and taking over. But I wanted the music to feel more organic and spacious, while the lyric was anti-technolgy. But I used a robot voice to deliver the lyric. In so doing, i was trying to communicate that Technology is so intertwined in our lives, that even when we are anti-technology, we use technology to communicate that sentiment. You can check out the sample on this page, it's called Statemeant and isnt "finished" but I submit it as an example, for better or worse.
Congruence. The music and thematic elements and the lyric need to have congruence. They have to line up, or purposely NOT line up, and by doing it on purpose, they are lining up with the intended message. This is an important concept to grasp. The whole song is the message we are communicating as songwriters, not just they lyric and not just the music.
So what are some examples? Some famous examples might be Nirvana songs. The content is aggressive and reflective of the lyrical content. A very simple, and prefect example, if a bit outdated is Bobby McFerrin's "Don't Worry Be Happy". Like it or hate it, it communicated a message and did it well.
Perhaps you have some ideas of your own, or some examples. I'd love to hear them. What songs are good examples of congruence, or Incongruence on purpose, or places where its a bad fit and the goal of congruence wasn't achieved?