I hope I am posting this in the correct stack exchange,
I am currently researching on musical instruments, particularly the Erhu and Shamisen, and have come into 2 interesting constructs. I have noticed that on the "drum" part of the instrument there are special carvings , supposedly to improve sound quality. I am not sure what it is referred as in the Erhu, but on Shamisen it is called ayasugi bori.
To me a layman, the Erhu one seems to make sense, I 'm a bit dubious on the Shamisen, but I would like to know do they actually improve column or sound quality of some sort?
The first image is the Erhu, and the second is the Shamisen