It sometimes helps to think of the bass line as a second melody.
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As you work on your next song, it’s a good idea to think about how the melody line and bass line work together. That concept of the melody and bass line “working together” may not have ever been something you’ve given thought to before, and you may wonder what those two lines can possibly have to do with each other. But considering how they move together can give power to both lines.
Sometimes a bass line is not so much a line, especially if it sits for long periods of time on one note. That’s especially true for fast-tempo songs. But other songs, and particularly ones that are slower in tempo, will have a bass part that moves a bit more, and in a sense, acts like a duet with the melody.
When you compare a melody and a bass line, there are four possible ways that the two can move relative to each other:
- In parallel motion (i.e., they both move in same direction by the same intervals.)
- In similar motion (they both move in same direction, but by different intervals.)
- In oblique motion (i.e., one line moves to a different note while the other one stays on the same note.)
- In contrary motion (i.e., both lines move in the opposite direction.)
This may seem like analysis overkill, but it’s important. The ideal situation is that a bass line should show a good mixture of the four different relationships listed above.
That way, you create a sense of independence between the melody and bass. There are usually several melody notes for every bass note, so here’s how you can analyze your song to allow you to examine the relationship between melody and bass:
- Play the first two chords of your song, and make note of the bass notes for those chords.
- If your melody uses several notes per chord, make note of the last melody note that uses the first chord, and the first melody note of the second chord.
Now do the same thing for the next time a chord changes. Ideally, you’ll notice that there’s a good mixture of motions: sometimes you see similar, sometimes contrary, sometimes oblique and sometimes parallel.
If you find that you tend to you see the same relationship too much (e.g., you might see that your melody and bass move in similar motion most of the time), you can fix that situation in one of two possible ways: 1) Choose a different chord; or 2) put one of the chords in an inversion (which means to put a different chord tone in the bass, creating what’s often called a “slash chord”).
Mixing the four different types of motion together ensures that your music “breathes”, and it actually creates a sense of transparency in the musical texture.
Once you’ve done that with your own music, try taking some of your favourite music and do the same kind of analysis. This kind of scrutiny between melody and bass is something that Classical composers did as they worked on their music, and we can learn from their example.
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