Interesting site! (I replaced "koto" with "www" in the URL to see their whole range of offerings; sorry to see they've nothing for shami...which reminds me, I haven't gotten the dern thing out for nearly a year, yikes!)

Any idea how commonly used that notation is? The few traditional koto scores I've seen were incomprehensible. Part of the mystique (or tradition thereof?), no doubt....

I've seen the number notation used before for koto (and shakuhachi too), but generally as a "beginner's alternative" to the real stuff, which uses columns of katakana to the same basic effect... it's not that difficult once you get the hang of remembering which tuning you're in and which character means which note on the scale. (Not that difficult to read, I mean, I still can't actually play.)

By the way, I didn't know you played shamisen...

鷹の爪隠しじゃ・・・じゃ・・・じゃじゃじゃじゃじゃん！