But don’t you have to answer the question whether or not the midi file makers and style makers have copyright in the work before you can talk about rightful compensation?

I would think that style makers, if they create a work that does not substantially sound like another song, they have the copyright to that new creation in a style. If that style is viewed as a new original work, then they would have the right to control modification of the work, any derivatives of the work and distribution of the work.

I would agree that the sheering of styles made by an independent style maker will hurt the individual style maker and probably put them out of business. However, I don’t think it will hurt the manufacturers as much because as part of the keyboard the majority of people want internal styles.

As much as I would not mine an arranger without any preset styles, I don’t think that will happen because the majority of the arranger market wants every thing done for them already. So a keyboard manufacturer would not make a keyboard without styles because they would not sell.
From a performer’s viewpoint, it is better when the performer creates the style because it will fit the playing style of the performer and will give an individual twist to the style.