It's not a simple question of the piano being out of tune 'with itself'... I was playing on that recording in the old ( and much missed) Kingsway Halll, and remember it well.
The piano, if you listen closely, is tuned to EXACTLY A=440 hz ( those were the days) but during the early 1970s there was a tendency for the LSO's overall pitch to 'creep up' higher than that, despite the best efforts of the superlative 1st oboe, Roger Lord.
So, for much of the time, some of the woodwind ( not the oboes!) and strings are playing at about A=441hz .
I was trying to 'stay with' Roger Lord, but now, 40-odd years later, my horn solos with the orchestra do sound a tad flat,

but, dare I say it,quite well in tune with the piano in those few moments when the music turns into a 'piano/ horn' duet. ...
