Mystery neighbor's sporadic performances give pointers on excellence

It has happened a few times in the three years I've been living in my apartment.

I'll be sitting in the back room, usually with the windows open, and suddenly hear the faint tones of a piano fluidly rippling from the bottom to top of the keyboard and back again.

Each time, that was merely the prelude. It's usually followed by one or another lightning-fast study piece where the player's fingers race over the keys as though they're being chased by flames, and after that another florid work where, however, the pyrotechnics leave plenty of room for expressivity.