1. Composing is completing the creation of musical content. A simple melody cannot determine the content that music wants to express. The overall sound of the music, including melody (if there is a distinct melody) and percussion (if there is percussion).

Arranging is to expand the expression of the music without affecting the main melody and content of the original song. In modern music, especially pop music, composition and arrangement are often two people, because many composers only have the grasp and inspiration of the melody, while the arranger has more skills in how to embody the melody. To put it simply, the composer gives the skeleton, while the arranger gives the flesh and blood.

2. For composing, you can use staff notation to write down the music. For arranging, you need to download some arranging software and sound sources.

3. Composition is the basis of arrangement. Composition refers to making the main melody of a song, that is, the score, and arrangement is based on the main melody, adding drumbeats and harmony in appropriate places. Various electronic effects, etc.

Extended information

Some composers will also do some music business for the purpose of profit, targeting the public, enterprises, etc. Most people who have not received music education or composition training only have a sense of tunes and can only hum some simple tunes, but do not have the ability to compose or produce to complete music creation and audio generation. Because the tune cannot reflect the complete musical form, nor can it determine the music content. So they will pay the composer some compensation to arrange the music.

When many people think of the word "arranger", they think of a certain profession or job in popular music creation. In fact, there is no necessary connection between the two. It may also be a customary understanding caused by business operations. The music arranged by the composer can be pop music, classical music, ethnic music or other music types.

Baidu Encyclopedia - Composition

Baidu Encyclopedia - Arrangement