The responsible bass player

"A chord is not a chord until the bass player decides which note to play" — a line usually attributed to Sting, and it packs the whole idea of reharmonisation into one sentence.

If you play, you already know this: a C major triad — C–E–G — turns into A minor by adding a single note underneath. A–C–E–G. Nothing at the top changes. Only the foundation does.

A simple exercise I used to do in my early days on bass was to play covers while changing the bassline under the same chords. Most of the time I made a mess of it, but every so often something new turned up. It sounds like fiddling, and it's the thing that opened my ears to harmony and to how notes and chords actually relate to each other.

_Adam Neely on bass note reharmonisation — "a bassist's secret weapon" — with played examples._

Studying scales and harmonic relationships stays essential if you want the substitution to be right, but the point is to get your ear used to different sonorities by playing with them, until you understand what the instrument can really do. My advice to anyone rehearsing a cover: take ten minutes and play it again with a few chords changed underneath the same vocal line. You'll find a new world in there. (If you want to go deeper, there's a whole strand of reharmonisation carried forward by bands like Dirty Loops and Sungazer.)

Why we hear the lowest note as the fundamental

The explanation gets complicated quickly, so let's try to stay out of the academy.

Low-frequency sounds arrive with more force than high ones: their wave is longer, dissipates less energy in the air and travels further before running out. It's the same reason the rumble of thunder reaches you from miles away while the sharp crack of a nearby strike dies out much sooner.

Now, every sound is made of a series of sine waves at different frequencies and amplitudes, tied together by a mathematical relationship. The starting one, the lowest in frequency, from which the others are generated, is the fundamental.

When you tune a guitar, the A string has to vibrate at 440 Hz to be in tune: that's the fundamental. The other frequencies grow out of it. Those that are whole multiples of it are called harmonics; the rest are partials, and they're what gives an instrument its timbre. This is why we can perceive the fundamental of a chord even when no instrument is actually playing the root: the sine waves reaching our ear still stand in a relationship that points back to it.

We perceive it, though we can't always put a name to it. People with perfect pitch manage better; people with relative pitch — which is nearly all of us — get there anyway, with some practice and an instrument in hand.

It also explains why we hear wrong notes most clearly in the low register. If a bass player plays a note outside the harmony, the dissonance is obvious to everyone in the room, even to people who couldn't name what went wrong. They just know something did. The reason is that on top of the wrong fundamental you get harmonics and partials fighting the rest of the band — a small disaster for the ears.

So the bass player's role is decisive for how a melody is played and read, alongside a rhythmic job done in close contact with drums and percussion. All of which makes the bass — electric or upright — a less soloistic instrument than others, without making it any less of a lead.

A dirty job. A responsible one.