I heard from a friend years ago that one of the Rebbes from Gur (possibly the S'fas Emes) wrote a book describing the proper pronunciation of Hebrew letters and words. I am not able to find any trace ...
How does one pronounce the name of the sefer בני יששכר ? I've heard people pronounce both sins -- so it is Ysoscher. (There is also a common custom to pronounce the name יששכר with both sins the ...