I'll bite Chas .

No special arranger keyboard lessons are necessary . If folks are struggling with timing then ordinary keyboard / piano lessons are not going to help so arranger lessons won't help either . If someone can't hear that certain lead instruments don't sound their best played as a chord throughout an entire song then it might be a struggle to teach them how to get the best out of these fabulous instruments However there is a valid argument for arranger keyboard lessons as many great musicians miss the opportunity of using an arranger because they don't know what they are capable of . Have a listen to this tutorial by Peter baartmans . I wish the whole session were available on dvd as I would surely like to hear his tips . http://youtu.be/-50DHkxtoAw