Question from Cream: What are the roles of 作曲, 編曲, 作詞 and 監製?

Answer (to the best of my knowledge)
Written out to give some sort of credit to the original creators of the song as respect ^^ Also, some people like to know the information; e.g. an artist may have composed, arranged and written the lyrics to their own song.

作曲：___
zuo qu/jok cook
Composer - who composed the music

編曲：___
bian qu/peen cook
Arranger - who arranges the music into what hear in the song

作詞：___
zuo chi/jok chee
Lyricist - who writes the lyrics to the song

The following are used mainly for songs that also have a music video released:
監製：___
jian zhi/gaam jai
Producer - used where the filming and production of a music video is involved

導演：___
dao yan/do yeen
Director

Other notes
填詞：___
tian chi/teen chee
Lyricist - as above

When I just use 曲:___that person/people did both the composing and arranging of the music and 主唱/演唱 tells you who is singing the song.