Familiarity with the job of music arranger, Ahmed Almuhandes says in this regard
Who arranges the music?
As musicians get closer to playing a piece of music, they have to decide how to interpret it. These notes may only exist on one page, but before they can be written on the page, a lot of things have to happen for this art project to come to fruition. A good music arranger is often an integral part of this artistic process.
The music arranger can work with a complete musician or orchestra with a choir and conductor. Obviously, the more parts involved in the composition, the more complex the music arrangement. However, in any case, the music arranger must work to determine the exact needs of how and when to play each note of the piece.
The music arranger answers the questions of what instruments should be used, what melodies and harmonies should be used, how the melody is harmonized, where to add the decorations to the main melody and where not to do so. . These are just some of the musical and artistic choices that a music arranger makes. In some cases, the artist may ask a professional music arranger to arrange a piece on a different key or even a different genre of music.
For example, a tuner might turn a Bach work into a jazz performance. If the task of arranging music is done correctly, a violinist can play the sheet music to play his rock songs. Or, for example, a regulator may simplify a complex task, so beginners can get started sooner without getting discouraged.