When using a copied built-in style from an earlier KN, via the Composer, the actual rhythmic patterns within the style will be the same. However, since the actual instrument voice samples used within the style will be different on the two KNs, the overall sound of the transferred style will be slightly different. This will probably be most evident in the KN3000 / KN7000 comparison, where the KN7000 samples are in most cases, better than the KN3000. You would probably notice less difference between KN6xxx and KN7000.
I'm not saying that a piano will become a flute or a trumpet become strings the actual instrument assignments will remain the same - just probably better quality on the newer KN.
Another thing to be aware of - if you are transferring a Composer style from an earlier KN and that style has been edited to include one or more voices from Sound Memory, then the Sound Memory must also be transferred to the later KN. If this is not done, then some very strange effects may result, depending on which sounds are resident in the later KN's Sound Memory, at the particular location accessed by the style
Again, since the Basic sound samples used in the edited Composer style of the earlier KN will differ from the Basic sound samples in the later KN, there will be a difference in the sound, or sounds, when the style is played on the later KN.

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Willum