A very informative session. I(http://session.In) am looking forward to next week's session.(http://session.In) In (http://session.In)this evening's session on the Pathetique, it was pointed out that Beethoven's piano keyboard lacked the top and bottom octave-and-a-half of range found on the modern piano. I have read that a couple of later developments in 19th century piano design made an expanded keyboard possible. One was the metal/iron plate that was able to support the added tension of additional tuned strings and protect the wooden rim and soundboard from collapsing under the pressure. A second was cross-stringing, that allowed all added strings to fit within the piano case without having to increase its width. You can see inside a modern piano that the base strings are installed over and diagonally across, rather than adjacent and parallel to, the midrange and treble strings.