well, i don't do mobile recording, but in my studio, i have a wierd way of micing up grand pianos but the results are the best piano sounds i've ever heard

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here goes:
I use a
AKG C414 on the left hand side, more towards the bass notes, and i also keep a AKG Solidtube a few notes away from there.
The solid tube's pickup range is quite wide which works well for a piano.
Towards the midrange of the piano, i use a Rode Classic IIfor the middle of the piano.
I like to have a crisp sound for the higher notes so i use whatever comes to hand for that. All the mics go into a really beautiful (and huge!) Neve desk. most of you will know that the pre amps on Neve's are amazing, and thatt brings warmth to the piano sound. On the desk, i'll bring up all the mics and just blend them in. I make
the Rode Classic II take priotiry as it's in themiddle of the piano and has a great range and gorgeous sound. all the mics are panned appropriately and have no eq changes. I don't usually like using compression on piano tracks cus it take all the dynamics away.but sometimes, i use a little compression from a Urei or a Focusrite. The plug ins on Pro Tools are quite good but if i'm recording analog, my compression stays analog aswell.
well, that probably doesnt help youmuch cus you might not have the same equiptment as me, but it might guide you as to how studios mic things up.