If I sit in front of a piano, in waking life, and pretend to touch each key I can mentally hear each note. Through simple memory association and countless hours of practice, it makes sense that this would arise. How this translates into the dream world is not a matter of possibility - as mentally in waking life I could do it. It's definitely possible. However, in the dreamworld, accuracy is seemingly never the same as waking life (most likely because it's largely controlled by your ever-changing unconscious desires and expectations).

I have tried this in a WILD before on my house piano, and the notes individually were seemingly accurate to waking life. However, when I played a tune I unconsciously expected to play it perfectly (this expectation affects the accuracy) - Hence I can press any key at this point, and I will hear the tune perfectly.