MK plays the keyboards well too, he just likes the guitar more
According to Mimmo Carrata who has more knowledge than all us put together, MK wrote all the piano/keyboards arrangements and AC
didn't create anything of his own during the DS
Word of ghost.
My bet is that's Mimmo opinion as well. I know musicians whose opinion is that most of that piano/keyboards parts and arrangements needs of a knowledge of the instrument that can't come from a guitar player no matter how good he is.
1) That theory doesn't work when you have a genius composing
2) MK knows how to play the piano
Mark can play the piano, that’s true, just like Guy can play guitar and Richard can play bass guitar. That doesn’t mean much. I highly doubt Mark’s piano skills would allow him to write, for example, the piano parts Alan played in TR.
That being said, we have a few options here:
1. Mark played it on the guitar and Alan adapted it to the piano;
2. Mark gave Alan the key, chords and so on and Alan came up with everything;
3. Mark gave Alan ideas and directions and they worked together to perfect it.
1 and 2 sound rather unlikely to me. I’d bet on 3.