What is the difference between being a musical composer and being a musical arranger? While a composer creates the original melody and harmony the arranger takes the composition and filters it thru the melody, harmony, bass lines and rhythm of the style of music and pairs it with the intended ensemble. In a lot of cases the distinction between the two is very fuzzy. When Beethoven wrote the 5th Symphony he composed it while arranging it for the orchestra at the same time and at least in Beethoven’s case made it almost pointless to do anything with the work other than to leave it as it is. The 5th Symphony would not work for Peter, Paul and Mary or Maroon 5.
For me it brings up the question of the symbiotic relationship between a songwriter (composer) and an arranger in modern day popular music. If you look at the credits on Michael Jackson’s Thriller album it lists a variety of composer’s, arranger’s (8), instrumentalists, etc. The arrangers are listed as sectional and Quincy Jones is listed as the producer which in this case means one generally in charge of the entire production. I would put forth that Mr. Jones was actually the arranger of the entire album. He took a wonderful group of musicians, oversaw their efforts and channeled them thru his vast amount of musical experience, knowledge and God given talent. Thriller would not have been the album it was without the incredible talent and composition of Michael Jackson (and others) and the amazing arrangement and production skills of Quincy Jones.