Composition vs. Arrangement

[sothilander]

This is not about the following 4-part setting I wrote and uploaded recently:
https://imslp.org/wiki/Wir_pfl%C3%BCgen ... ham_Peter)

But it is also a general issue.

I contribute mostly new and own (mostly) 4-part settings to existing melodies by other, sometimes unknown composers.
I tend to call this a "composition" and would like to see it in this category of mine and rather not as an "arrangement"
under the name of the composer of the melody.

In particular in the case above: The composer of "Wir pflügen und wir streuen"/"We Plough the Fields and Scatter" in not known,
it was a Hanover songbook from 1800 and is supposed to be by Schulz.
The EG https://en.wikipedia.org/wiki/Evangelisches_Gesangbuch does not name him as author, but writes "Hanover 1800" instead.

[sothilander]

To further illustrate my point: What is an "arrangement"?
Typical examples:

1) https://imslp.org/wiki/Jerusalem_(Parry ... _Hastings)
I arranged Jerusalem for mixed choir (SATB) using the existing score (rather the piano reduction).
No new music, but music rewritten for different instruments/voices.

2) https://imslp.org/wiki/Ich_steh_an_dein ... Sebastian)
I took Bach's melody and basso continuo bass part and wrote a third (middle) voice (mostly) using the continuo figures.
The harmonization is mostly fixed by melody and the figured bass.

3) https://imslp.org/wiki/Das_K%C3%B6nigsl ... lf_Eduard)
I took an existing male choir song and transposed it and changed some notes to create an arrangement for mixed choir (SATB).

However, whenever I write an entirely new harmonization and parts to an existing melody, I would call this a "composition".