These are least four teachers and musicians who practise traditional Japanese instruments and love to teach and share both in traditional and modern settings. I believe shamisen resources or teaching is available on #2 and #4. I would use #1 for biwa history and #3 for sanshin history.
1.Satsuma biwa history and info actually helps to those learning Japanese strings in general and some suggestions if you want to study some related chanting and background…nerdy me likes this…biwa vocabulary and plenty of performance clips by Junko Ueda
Chikuzenbiwa and Yoko Hiraoka.(Colorado)…Kyle san has one of her concert biwas…
Okinawan Sanshin and Junko Fisher (New York)
Reiko Obata …San Diego CA Kotos and More