I heard this on NPR this morning, and I was glad to hear that even something as standard as the grand piano still has room to grow.
Apparently there is a piano maker in Australia (Stuart Pianos) who decided that the 88 key piano as we know it is insufficient. Instead of only going lower by adding nine additional notes beneath the low A key, they also tacked on five
It sounds like the main benefit to the overall sound is that the notes' harmonics have more room to play. Result: a potentially fuller and crisper sound. I'm just curious what Rachmaninoff could have done with the extra notes.
Listen to the story, or read the transcript here.