Harmonic Density

In this article, I will discuss harmonic density in rhythm, what it is, and how great guitarists and songwriters use it. Harmonic density relates to chord changes and its related harmonic rhythm. How often the chords change can set up an expectation. There are a lot of songs that operate on a four-bar phrase with four chords going around and around. If that four-bar phrase were done for a section and then played stretched out or compressed, it would change how the music feels, even if playing the same four chords. 

The following is a good exercise to try out. Create a four-bar phrase with a one-chord bar and then collapse it so the four chords happen in 2 bars. Then, stretch it out and see the effect on the melodic phrases. An example of this that matches up well with the song's tempo is “Hallelujah,” the Leonard Cohen song. Listen to this song or play it and note how he has more than one chord per bar for most of the verse. Then, he slows it down to one chord per bar in the chorus, giving the listener a little pause for contemplation. The whole song builds to that moment of the chorus, not a big chorus like the kind in a pop song, but offers a more meditative quality. By slowing down the rate of harmonic change to one chord per bar where it had been two chords, or in some cases three in the earlier section, gives the song a shimmering contemplative quality. 

Another example of changing harmonic density is the 12-bar blues arrangement. Try to visualize where the first four chords are in a top section for four bars. The I chord played for the four bars. The next 4-bar section section is the IV chord for two bars back to the I chord. For the last four bars, you will change chords for every bar. This structure gives the sound a big push of energy at the end. Then you go around to start again with the I chord played for four bars, etc. 

The typical Twelve Bar Blues arrangement always starts with the harmonic density of the rhythm slow. Then it speeds up over the next four bars and speeds up again at the end for the last four bars. The harmonic density rhythm speeds up towards the end because it propels you forward and then takes you back to the beginning for the resolution to the I chord. 

In classical music, you hear this often before cadence points. If you have a sixteen-measures section of music, you would often hear the rhythm's harmonic density change right before the final cadence. It may have started with one chord per measure and moved on to two chords per measure or even four chords per measure as you get closer to the cadence at the end. The cadence returns to the one chord after speeding to the multiple chord changes. The harmonic density comes faster and faster because it builds more tension. 

The harmonic density of rhythm has the word “rhythm” in it but we do not play any faster. You could change the rhythm, but if you keep the rhythm with eighth notes, quarter notes, or sixteenth notes the same but change the rate or density at which the chords change, it is the harmonic rhythm that speeds up. It creates a lot of tension even if you are not accenting with dynamics or in other creative means. 

Harmonic density or harmonic rhythm is a very useful tool that has been around for centuries. Classic rock people have and do use it. Think about “Little Wing” by Jimi Hendrix. The chord changes are four beats in the whole first half of the song. Then, towards the second half, it's just two beats per chord until the last chord, which is 8 beats. It gives you the sense of feeling like you're moving away from where you just were, and it's taking you somewhere else. 

The David Bowie song “Changes” and  “Let It Be” by The Beatles are great examples of the harmonic density of the rhythm changing as the songs progress. These examples compress the chord changes into a shorter time and then give a little tiny breather, which draws you into the song well. Listen to these and other songs to try and identify the harmonic density/rhythm utilized in the song.

If you want to learn another excellent rhythm guitar skill, check out my FREE lesson on how to weave lead guitar melody lines to your rhythm guitar playing here: https://rhythmguitarlessons.net/Pro.

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About Mark Turko: Mark Turko is a professional guitar player and instructor with over 30 years of experience and teaches guitar lessons online.