Orchestral Voicings Part 14: The Influence of Dynamics

One factor that is often overlooked when constructing voicings for orchestra is the dynamic degree that it is going to be played in. The same voicing played in pp can sound very different in ff and by that I don't just mean louder.

In fact, it could happen that a perfectly fine sounding pp voicing becomes super muddy in a higher dynamic degree.

To understand why we have to dive a bit into physics. I'm sure most of you know the principles about harmonics but for the people who don't here's a brief (and ridiculously incomplete) explanation:

Every tone that we hear consists not only of one frequency (the pitch that we usually perceive) but of several frequencies that all align in a specific relative distance to the fundamental pitch. This is what we call harmonics or overtones. The balance and volume of these harmonics have a big influence on how we perceive a texture of a tone as every instrument comes with a quite unique balance between these harmonics.

These harmonics almost always align in the harmonic series on top of the fundamental. So the next frequency will be an octave, the next an octave and a fifth, the next two octaves higher than the fundamental.

For further deeper explanation check out the Wikipedia article on this topic.

In general, one can say that the louder an instrument is played, the more harmonics will be introduced to its sound and the brighter it will become. This effect is particularly strong with brass instruments who have a significant change in timbre over their dynamic spectrum. With woodwinds the effect usually is not as extreme and with strings even less.

To demonstrate the effect, here's the same tone played by a solo horn, once in pp and once in ff. I adjusted the volumes so we can focus only on the timbre difference.

https://soundcloud.com/robin-hoffmann/horn-pp-vs-ff/s-lSjVotsK08X

If you run this audio through a frequency analyzer, you will get this:

Left is the pp note, right the ff. The lowest orange line in both is the base frequency with the higher orange lines being the harmonics. The brighter the line, the louder the frequency in the mix. You can see that both base frequencies are practical identical in volume but while in the pp sound we can only observe a few higher harmonics, the spectrum in the ff note is very full with a lot of harmonics up to 20khz.

Of course, I chose a drastic example here and it would not be as obvious and extreme with for instance a violin, but with pretty much every brass instrument and a lot of woodwinds you get a similar effect.

This difference has a drastic implication on voicings. We already touched on that subject when we discussed Low Interval Limits, but the implications of this concept are even more far reaching.

We have to understand that every note that we write doesn't include just this pitch that we're writing but in fact all its harmonics (in varying degrees of volume). While our ear is trained to not hear these frequencies individually, they are still there and in complex voicing situations can have a drastic influence on the perception. The lowest few harmonics span a major triad over several octaves so when I'm writing a c, I in fact generate a c major triad.

As we saw above however, the dynamic degree has a strong influence on how strongly these harmonics will be present in the sound. As a consequence this means that the louder the voicing, the more additional overtones will be present. This has a big influence on the transparency of a voicing. In very soft dynamics, I can quite easily write complex voicings even in quite low registers that will remain quite transparent and understandable. If I however play that voicing at very loud dynamics, it might well be possible that I create so many additional harmonics that it becomes muddy and intransparent to a degree that it might not be understandable.

But also, particularly in major chords, the dynamic degree implies how much "chord material" we need in the voicing. For us as composers and orchestrators, a loud major chord needs far less harmonic support than a soft one, just because all the notes of the major triad will be present anyway. In fact "overharmonizing" the sound might make it less punchy and more thick. Another clear example of this concept are guitar power chords which technically are just a fifth but due to distortion and its added harmonics sound like a major triad. Similar effects can be observed for instance with loud fifth in trombones.

To demonstrate this approach in the real world, let's have a look at the iconic first Bb major chord of the Star Wars Main Theme. The following excerpt is a transposed score so you need to transpose in your head. Also warning: scrolling ahead.

(If you don't know that piece for whatever reason, here's a recording)

I think we all might agree that we perceive this chord as a properly balanced Bb major chord with all chord tones perceived at similar levels. However, the really interesting thing here is how little non-roots are actually in that chord. The only chord material here is provided by the violas (the third), the horns (with a brief attack of a Bb major triad) and the trumpets holding that really high Bb major triad for the entire length of this chord.

Everything else is root notes. In the woodwinds we don't have a single different pitch than Bb. Of course, Williams knew what he was doing and he wanted a punchy "in your face" opening. All these Bb that are sounding at this high dynamic degree of sffz, include the entire Bbmajor triad in their lowest (most prominent) harmonics, so they create harmonic material without writing it. So it needs only a few forces written on actual "non roots" to acoustically balance that chord for our ear. That very same chord in a soft pp would sound considerably empty and the very same loud dynamic with a chord that has considerably more chord material in the voicing would sound thicker, less punchy and less bright, overall feeling weaker than the way that it is written.

As I said, this drastic difference doesn't apply with all instruments. Especially when writing for strings you can be way less concerned about these things but especially in brass writing, it is definitely worth paying attention to this.

You might for instance be surprised how little harmonic bed is often included in voicings in so called "epic music" which live from loud brassy chords that often are just power chords or even just fundamentals and yet imply a rather full harmony. Minor chords and more complex harmony of course need essential chord tones to be played but could for instance live without an explicitly written perfect fifth in a voicing as it will be implied with the fundamental.

So the bottom line here is, especially when writing for brass, take your dynamic degree into consideration when voicing chords and adjust the amount of chord material accordingly. Of course it all depends on what you want as not every loud voicing needs to be as punchy and transparent as the Star Wars opening.

 If you want to read all the other parts of the tutorial series on voicings, click here.