I would also add something to this topic. An arranger is also defined by its hardware, I mean an arranger must have only ONE keyboard, otherwise it becomes an organ or probably a digital piano with arranger functions. What’s the difference between an arranger and a modern organ? Only the double/triple keyboard and pedals and consequently the way you play it and how you use it. What’s the difference between an arranger and a Clavinova?: the 88 hammer action keyboard. Actually the word “arranger” is an English word without an exact translation in my language. In spanish an arranger is called “arreglista the canciones” what would sound like “song composer” and some dealers still call it an “organ”.