What's the difference?
If you work in the music field, you will likely come across these 2 terms: arrangement and orchestration. But, what is the difference between these two? Let's take a look.
*Before we begin, I just want to say that this is my professional opinion. A project may have aspects of both, or other people may define these slightly differently.
In easy terms, orchestrating is taking a piece of music and expanding or shrinking it to fit a new ensemble. You don't make too many changes to the structure of the piece. Arranging is taking the source material and adapting it as much as you want.
But, let's go a bit deeper.
Orchestrating
Orchestrating is the process of taking a written piece and adapting it to a different ensemble. A common place for this to happen is in film scoring. Generally, due to the time constraints and size of the project, film companies will hire a team of orchestrators to assist the composer in realizing the final vision. Their job is to take the sketches of what the composer wrote and turn them into full ensemble pieces. For instance, let's say the composer wrote a melody for solo piano, but the final product needs to be turned into a full orchestra piece.
Orchestrating can also take place as part of the actual composing process done by the composer themselves. It is the art of taking the little version of your piece and spreading it out into a full ensemble. In my own writing I do this mainly one of two ways:
1. In real time while writing the piece. This usually applies to a large ensemble or full orchestra piece. As I am writing the melody, I'll hear it in the trumpet or cello and throw it into that part for later. I will then orchestrate around that part based on the sound I want.
2. After completing the initial composition. This happens with choir pieces, musical theatre works, or anything else that requires an expansion from a reduced score. Any choir work with accompaniment will almost always be performed at some point with just a keyboard. So to make sure it works, I start by writing for just choir and piano and then if I feel that there needs to be other instruments added to the piece, I will go back and put them in later.
Arranging
Arranging almost always comes after the completion of the work. It is taking the preexisting material and turning it into something useful for a new ensemble. Some arrangements are very faithful to the original work and others are very loosely adapted.
For example, maybe you really like Taylor Swift and want to play a new song of hers with your clarinet trio. Someone would need to make an arrangement of that song, since the original is not a clarinet trio.
Transferring from one instrument to another directly does not always work, because they are sometimes in different keys or have varying ranges. If you were going to play a piece for cello on the alto saxophone, it would need to be arranged, because those instruments are not transferable.
You have more freedom in an arrangement to do whatever you want to the music. You can completely change the genre, the harmony, or the instrumentation. However, you want to make sure that you leave the main pillars in place such as melody, chord progression, and lyrics.
Here is an arrangement I made of "Made You Look" by Meghan Trainor. I arranged it for a string quartet, for which it is not originally written. Also, I made the final chorus a bluesy section, which does not happen in the original song. The song is still recognizable, but it just got a bit of a facelift. You can hear the original here.
More Examples:
"Let it Go" Original
⬅️
Arrangement for Brass Quintet ➡️
(Totally different instruments with some rhythmic and harmonic changes)
"Rhapsody in Blue" Original for Solo Piano ⬅️
Orchestrated version for Jazz Orchestra ➡️
(Everything is essentially the same just spread out around the ensemble)
TL;DR
Are you expanding or shrinking the number of instruments playing a piece of music? Are you making minimal structural changes to the music, just redistributing it for more players? - You are orchestrating!
Are you changing the number of instruments? Style of the piece? Key and range of the song? - You are arranging!
Want to know more music making secrets? Check out more of my blog.