Explanation: The second most important feature of your music arranging (after rhythm style) is the choice of chords and harmonies. For this, we will write a chord chart. To start, create a printed musical score of the song. All you need is a melody line. If you can't produce this, simply draw a layout of the song with vertical lines to indicate each measure. Then write in the chord symbols. If you have a good memory, you can skip the writing part, especially if you're very familiar with the song.
To get a good sense for composing chord progressions, I urge you to spend some time listening to great classical composers like Bach and Beethoven. They change keys and chords left and right, but follow one guiding principle. It must be so smooth as to be practically unnoticeable. Jumping to unrelated chords without preparing the listener can be jarring and distracting. The great composers prepared their chord changes in advance, so that when it happens you feel a sense of release and relief.
Another good example of changing chords often with proper preparation and sensitivity is the song " Oklahoma," from the Rodgers and Hammerstein show. It changes keys almost every measure, but it does it so consistently that we are anxious to follow the song along. Sometimes, pop songs may just transpose up a key to revive flagging interest in a repetitive melody. In my opinion, that's a cop out. Use with caution.
Spend time working on a fresh, satisfying chord chart, as it is key to good music arranging.
Next: 4. Create your grooves.