Chapter 4 now complete

The gap left by attacking Chapter 5 before Chapter 4 has now been filled in. I think it should now read continuously from the start to the end of Chapter 5 (so far). Some loose ends to be tidied up, though.

Chapter 5 taking shape

Chapter 4 is on hold because of a need to get Chapter 5 drafted. That chapter now has a lot of content, mainly about plucked-string instruments but a bit about the vibration behaviour of violin bodies as well.