The effect of the lower octaves on the left and the upper octaves on the right is a very common result of studio miking techniques used for upright pianos. In the early days, most studio engineers for jazz labels placed two mics in spaced fashion just over and in front of the piano's open top--one over the bass strings, and one over the high strings--and then compressed the signal to reduce excessive hammer attack. There were two other methods for uprights: miking the kick board area, and miking the upper sound board area. The two big problems in recording piano players in jazz ensembles was always leakage and resonances.
The art of miking a grand piano is far more complex, and depends on the style and preferences of the engineer. There are about 6 different basic miking positions, each yielding a different sound. But everyone has there own variations. Some engineers will space a stereo configuration one over the low strings and the other over the high strings either over the hammers (for a driving popular or rock sound) or at a distance outside the piano if leakage is not a problem (as in solo performances). If the engineer is aiming for transients, then he will use a condenser or extended range microphone, if he wants to capture the overall tonal balance of the instrument, he will use an omnidirectional mic. Should leakage be a problem, a cardiod or tighter polar pattern can be used.