Vertical and Horizontal Musical Development

One of the most essential things when writing music is to create a dramaturgy. This means to create some sort of development of your musical ideas, ideally leading to a sort of climax at one point.

This can be compared to storytelling where you create an exposition (in musical terms: introduce your idea/theme etc.)  and build up your tension towards a conclusion or reveal or climax and often building down from there towards an end.

Of course, there are certain musical genres and scoring situations that consciously (need to) avoid any sort of dramatic development but in general one could say that a lack of development very quickly can lead to your audience becoming bored and tuning out.

In music, there are generally two ways of development that can coexist but also exist each on their own.

Vertical Development:

A prototypical example of exclusive vertical development is a big percentage of what could be called "epic music" or "trailer music".

The structural development very often works in a way that a cycle of chords is being repeated several times with each repetition adding a new layer of musical information.

That could be simple things like adding more instruments or increasing the dynamic degree with the repetiton of the chord cycle or more complex things like establishing an ostinato, a rhtyhmic percussion bed, a melodic motif etc.

In a nutshell, it would be possible to create this dramaturgy by adding one more layer with every repetiton until reaching the climax.

A perfect example of this type of development is Time by Hans Zimmer. We have an eight bar chord progression that is being repeated again and again with every revolution adding a new element. In this extreme case every development step plateaus exactly on the same dramatic level throughout the entire chord sequence making a sponateneous step with the beginning of the next cycle. There is no gradual ramp within one cycle that is preparing the next cycle.

He keeps developing this progression in the vertical dimension by adding another layer each time - hence it would be called a "vertical development".

The application of this type of development seems rather straight forward and is relatively simple. In fact, a proven way to write such a piece would be to come up with the climax version of the progression and simply copy-pasting that several times in front of the climax and deleting one layer at a time.

Horizontal Development:

Contrary to the vertical development, the horizontal development works in a linear way. The increase in tension and dramatic growth is being achieved by developing an existing element or layer. This could for instance be a melody that is moving higher and higher, becoming rhythmically more active, employing increasingly larger intervals etc. But it could also be a chord progression that moves increasingly more towards tonally more remote places.

A great example for this type of development would be the buildup towards the climax in John Williams' Leia's Theme (3:13 onwards). There is a bit of vertical development happening here as well with more instruments joining in towards the climax but this section predominantly relies on horizontal development. Try focusing on the individually developing elements like melody, harmony, intervallic tension, rhythmic density.

Compared to the vertical development, horizontal development is increasingly more difficult and requires considerably more control over the music.

While the effectiveness and commercial success of exclusively vertical development is undisputed as can be seen at the genre of epic music that commercially outgrows the film score genre by far currently, it is dangerous to solely rely on it as it limits your musical expression. If your musical capabilites are limited to barely more than being able to build only a vertical development, your music will stay rather one dimensional.

It might of course be debatable why you would want to practice something that currently neither is commercially more successful nor particularly en vougue. In fact, it is obvious that there are a lot of composers out there who are commercially successful without having the skillset of being able to develop a piece horizontally. The answer as always is: the more control you have over your music, the better you will be at translating your intention to actual music. Consciously avoiding doing something that you however would be perfectly capable of doing is highly different than consciously avoiding doing something because it exceeds your capabilities. Even though you only might want to write vertically developed epic music in your life, being able to realize that and additionally being able to also know how to horizontally develop it will make you a better musician overall.  Just because Hans Zimmer decided to reduce "Time" to a repeating cycle of eight chords that keep building vertically (which could be very well understood as a conceptual idea considering the topic of the movie) doesn't mean he doesn't know exactly how to develop something horizontally.

As I said before, both types of development can exist on their own, but the musically most expressive way would be for them to coexist simultaneously. Developing that much control over music that for instance in a build-up every single element of your music supports the idea of the build-up (as can be seen spectacularly in the JW example above) and not a single element in the music behaves anticlimactic requires immense amounts of practice and experience.

One essential key to this is to realize and understand that there are these two types of development and becoming critical of one's own work to consciously know and decide which of the two should be used to transport your intention.