by Josh Cottell

I sit down at the piano and play two chords. It’s a C^7(♭9) leading to a F^▵(add9). Damn! That’s crunchy.

Hearing these chords would make many think immediately of jazz. But why? What is it about these chords that makes us think of jazz? The answer to this question is in the essence of the chords themselves, their harmonic makeup, if you will. Behind any interesting harmonic pattern, there is one feature that truly defines the style of a piece: dissonance. Originally meaning the suspension and resolution of a non-consonant interval, dissonance is a concept that has been used from as early as the 16th Century right up to the present day, in increasingly varied ways.

In the early 20th Century, when jazz was moving to the forefront of the popular music world, dissonance continued to be explored. The additions of sixths and sevenths to common harmony provided a wider variety of opportunity for musical colour. Even in the early days of Dixieland with the likes of Louis Armstrong and Jelly Roll Morton, these enhanced chord changes can be heard. But these additions are not just used randomly and fleetingly – each are still used carefully and to great effect. Voice-leading plays a huge part in the formation of a correctly-working accompaniment and the dissonances still often follow the original rules of the 16th Century – you can’t just add a note in willy-nilly and ‘jump around’. Of course, the clarity of these dissonances are different between jazz and early music – but that does not mean the thoughts behind them are not the same.

‘But Josh’, I hear you ask, ‘Surely some of these ideas are just as common in later classical music?’ (And if you didn’t ask that, you’re going to get an answer anyway.)

Well, you are technically right. The perhaps more commonly known classical examples of dissonance come from serialism, a genre popularised by composers such as Schoenberg, Webern and Berg. Their use of dissonance stood out among early 20th-Century composers for its almost unrestricted nature. (The fact that it was very restricted indeed is another matter entirely.) Going even further back in time, one can think of impressionist composers such as Debussy who again used ideas that rejected traditional western harmony. If one listens to this music, there are definite similarities between the additive harmonies used here and that of the chord progressions found in your favourite jazz standards.

But again, we ask ourselves: ‘Why?’ The answer is that all these composers, whether they be Debussy, Schoenberg, Gershwin or anyone in between, were all trying to create one thing: tonal colour. These colours, of course, vary dramatically across styles of writing, but to create the colours, dissonance had be used more freely.

The use of the concept in jazz goes beyond just the simple harmonic ideas you see in the chord symbols. Soloists are there because they want to stand out, they want to show off, they want to create interest. The way that they often do so is through dissonance. When done well, this can create some of the grooviest licks there are – just listen to some John Coltrane and you’ll get the picture.

People (often naïvely) say that ‘in jazz there are no such thing as wrong notes’, but there is always a point where too much dissonance or too little knowledge of dissonance can make for a rather unenjoyable listening experience. That said, too little dissonance at all just makes the music sound bland. For pianists, who often repeat the same chord sequence, there is a point of mind-numbing boredom. This is where the good-old sixths, sevenths, ninths, elevenths etc come in handy to create that authentic jazz sound. You never know, they might just throw in a tritone substitution to get the rhythm section really raving.

I think the key point I’m trying to make is that dissonance is part of the essence of jazz. It is deep within the heart and soul of what the genre is and, without it, you would not get the sound you look for when you click on that ‘Jazz vibes’ playlist on your Spotify.