Written by Gary Ewer, Senior Instructor, Dalhousie University, from “The Essential Secrets of Songwriting” website.
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It is a very useful exercise to sing through your latest song, accompanying yourself with just the bass line. How melodies and bass lines interact is tremendously important. I’ve seen it happen that songwriters spend a lot of time trying to create vocal harmonies, but having no success because there’s an underlying problem with the outer voices. So here’s what that’s all about.
Even several hundred years ago, how melodies and bass lines intermingled was of great importance. J.S. Bach, for example, wrote a series of what he called “Two-Part Inventions” as a way of teaching his students how to have two lines work together. And for very important reasons, it’s vital to consider the bass line a kind of “alternate melody”, something that works in partnership with the real melody.
There are four ways that melody and bass can move in relation to each other:
- Contrary motion (for example, melody line moves up while bass line moves down.)
- Similar motion (both lines move in the same direction, but by different intervals; for example, the melody might rise by a whole tone, while the bass rises by a perfect 4th.)
- Parallel motion (both lines move by the same distance in the same direction; for example, both lines move up by a minor 3rd.)
- Oblique motion (one line stays on the same note while the other line moves up or down.)
In my opinion, you can get a bit obsessive about this, so I’d recommend only dissecting your melody and bass line if you hear that there’s a problem that you can’t put your finger on.
When you sing through your melody, accompanying yourself with just the bass line, you should be noticing a fairly even mixture of all four types of interaction, with probably a preponderance of oblique motion. This is because it’s common to have a bass note last for several beats while the melody is changing above it.
So what are the signs that something sounds a bit off with the melody and bass? The biggest problems come from the bass and melody moving in the same direction.
If your bass and melody both rise by the same interval (i.e., move by parallel motion), it can create a stark, “hollow” sound if the interval between the two lines is a 4th, 5th or octave. So unless you’re trying to create that hollow sound, you’ll want to avoid parallel 4ths, 5ths or octaves.
Thirds and 6ths are intervals we tend to think of as “sweet” sounding, with a natural warmth, so having parallel motion between melody and bass that features 3rds or 6ths will not cause problems.
Here are some examples (sound samples open in a new browser window) :
As you can hear, there’s a bareness to the parallel 5ths, so you’ll only want to use that kind of interaction if it’s the bare quality you’re looking for. But in my experience, the quality of sound that comes from parallel bare intervals causes problems especially when creating backing vocals.
So the general guideline here is that if you find that you’re hearing a hollow quality to your song, and you can’t seem to put your finger on what’s causing it, it’s almost always attributable to how the bass and melody are interacting.
Try singing through your song slowly, and when you get to the problematic spot, make careful note of which notes are being sung, and compare them to the bass line. You’ll likely discover parallel 4ths, 5ths or octaves as being the culprit.
You’d be surprised how close your songs could be to being hit songs. Learn all the essential secrets of great songwriting by clicking here.