Is arranging music composing?

Basically, me and my composer friend have been arguing about this, so I wanted your guys' opinion.
My argument is that basically that composition is coming up with an original idea, and arranging is making a play upon an idea. Therefore, arranging cannot be composing. However, he's saying that since it's presenting music in an original way, it is composition since it is original in the sense that they're showing something old in a new light, like a new arrangement of an old song, like Caravan or Pachelbel's Canon.
I just wanna see what you guys think.
 

I think they are related but different things. Composition is coming up with the music itself but arranging is a reorganisation of that music, whether it be structurally, harmonically, orchestrationally, texturally, or some combination. I do think the lines are blurry though for example when arranging it is common to add new lines that were not present in the original or even cases like masses based on hymn tunes (e.g.; requiems) and pieces based on folk tunes (e.g.; Grainger's Lincolnshire Posy) that use the original material as a lose reference. 

I think the line between a new composition and an arrangement can be blurred in many ways.  For example, you could harmonize the original material in a completely new way or orchestrate it completely differently.  As @ConfusedFlourBeetle mentioned new melodies or countermelodies may be added or sometimes the new arrangement can take on the form of a final draft of a more sketchy and not fully realized composition.  I once re-orchestrated (and like I mentioned, re-arranged) a composition by a composer from Ecuador, Sergio Guerrero.  He came up with the idea for an orchestral Pasillo that combined the Minuet form with Pasillo rhythms (the Pasillo is the Ecuadorian national dance).  I thought it was a great idea and asked his permission if I could arrange my own version of the work.  It took many drafts where I constantly had to refine the material in his original composition multiple times.  It turned out really well I thought but there were also many original harmonic ideas that Sergio's version lacked or at best only implied.  I think that it could definitely be called a successful collaboration though.

Then there's also the potential for writing variations of a work which have much more potential for original ideas.  Or you could orchestrate a piano piece for full orchestra which definitely also requires ingenuity.  Or a combination of all of these:  re-arranging, re-harmonizing, re-orchestrating, or variations.

I always think this a bit of a non-question. To properly answer it, you first have to define exactly what you mean by arranging and composing - and this really answers the question itself. 

For purposes of illustration, would you define this piece as an arrangement or composition? It's a well known work for concert band that I have played a couple of times (on the solo flute part!)

They intersect with each other but aren't the same thing. If I take a keyboard part for a song, figure out the chord changes, and write down the chord symbols for guitar, I've done an arrangement but I haven't really composed anything. If I take the same song and do an arrangement for big band, I have to use my knowledge of how to compose for that ensemble to make it effective; and if I add an original intro, then I've definitely composed as well as arranged. And I'd argue that Ravel's orchestrations of his own piano pieces certainly qualify as distinct compositions.

Arranging is not composing.

They're usually part of the same thing for composers who initially work in short score. If instrumentation emerges as the composition evolves; text notes are made about what's doing what. Then again, perhaps they aren't and this is where arrangement begins, scoring the piece which can start at any time, not necessarily when the composition is finished. To me, it's still part of composing. Some people do go directly into score and it's probably more usual these days with daws and notation software but the same choices are still needed.

I'd understood arranging as converting a piece from one medium to another to preserve the spirit and feel of the original. It usually takes some compositional skills. Anyone who's tried to arrange a piano piece for full orchestra (or vice versa) will be well aware. For example. try scoring the opening bars of Beethoven's Pathetique Sonata by assigning notes literally to whatever instrument(s) can play in their range and it'll sound a mess. It needs creative thought. Fine, the arranger won't have to add original material but will often rewrite parts creatively. (reminds me of one of the entry pieces for my RAM diploma - set a part of a Chopin Mazurkas for a brass quintet.)

Same in the other direction: arranging a full orchestral piece for a solo keyboard. If needed, notes may have to be missed which needs judgement about what's important in the harmony. 

So, arrangement isn't composing but may need some of the skills of composition.

They are definitely related and involve a lot of the same thought processes, but they are not the same thing. Arranging is taking a preexisting work and fitting it to a different set of instruments. Composing is writing something with enough originality to be its own piece. In effect, I tend to think of arranging as "composing from a reference point" because of how the same processes are used in both arranging and composing. Now, this can be blurred sometimes, as sometimes an arrangement of a preexisting work becomes part of a separate piece or its own piece entirely. Take for example, these 2 pieces by Beethoven, the Septet in Eb Op. 20 and the Trio in Eb Op. 38.

The trio is an arrangement of the septet, and yet is considered a separate piece from the septet. And both of them have material in the third movement that was used previously in his Piano Sonata no. 20 in G major, which is just one of many examples of Beethoven recycling his own material.

This is just one example of composition and arrangement being blurred and there are some less clear examples out there than these 2 Beethoven pieces, but as I'm most familiar with Beethoven, I chose the septet and trio as my example of the blur between composition and arrangement.

As I'm experienced in arranging pieces for a variety of ensembles and by a variety of composers, I can say for sure that there are composers that fit perfectly or almost perfectly into a note for note reduction arrangement a lot of the time such as Haydn and Mozart. And there are others for which I almost always need to subtract a little and sometimes a lot to make the reduction feasible for the players, such as Beethoven. For expansion arrangements, Beethoven is still tricky and I still sometimes have to subtract, though not as often as with reduction arrangements. However, for Haydn and Mozart, I often have to add rather than subtract if I'm doing an expansion arrangement such as solo piano to string quartet or string quartet to orchestra. This could be as simple as doublings or as complex as an added countermelody. Indeed, even in reductions, I sometimes have to add to what Mozart wrote, usually by adding tremolos or Alberti Bass where there are long notes in the original score.

On 4/17/2022 at 6:26 AM, PeterthePapercomPoser said:

I think the line between a new composition and an arrangement can be blurred in many ways.  For example, you could harmonize the original material in a completely new way or orchestrate it completely differently.  As @ConfusedFlourBeetle mentioned new melodies or countermelodies may be added or sometimes the new arrangement can take on the form of a final draft of a more sketchy and not fully realized composition.

You make a good point about the blur between the two. Were Deryck Cooke and William Carrigan composing or arranging when they respectively 'completed' Mahler's 10th and the last movement of Bruckner's 9th Symphonies. It looks like an inextricable mix of both. The basic material was there but had to be filled out, extended, with a good musicological knowledge of both composers and the sensitive addition of new music to make the works 'make sense'; to make them sound as if they came from the original composers.