Roel, I listened to this piece and the performance is VERY GOOD!!!
While Greig has never been one of my favorite composers, I can tell your pupil did a very nice job playing this piece.
The recording seems to lack some real, clear definition in the lower frequencies. I have found that backing the mics off from the source doesn't really help much in this instance. The problem is in the diaphram of the mic.
There is an ENORMOUS amount of harmonics, sympathetic resonance, plosives...etc. happenning under the lid of a piano. Trying to faithfully capture and detail all of those is indeed difficult.
I have trhown every mic I have or have ever com across at my grand, trying to capture that detailed piano sound typical of classical playing. Good stereo micing techniques are critical to acheiving that, as of course is mic selection.
The best I have been able to do was from using a pair of TLM103's.
My second choice would be the SM81's. (read my other post in the mic forum for comparisions)
and finally, from my mic locker, I'd reach for the ECM8000's. I really believe you could pull off a very nice recording using these, but be prepared to spend a lot of time experimenting.
~Michael~