Music In Japan and Rokugan
Some Resources for Japanese Music
This page has a wealth of information on the styles and development of Japanese music.
Wikipedia also has a lot of information on the history of Japanese music.
There are also several articles on this site, one of which in particular could be interpreted as a Crab samurai's chant for safe delivery from the Shadowlands.
(On closer examination, however, Wikipedia's Japanese music index still has more articles than the above site.)
This site has all kinds of Japanese songs, with lyrics written in English script and musical information provided as well. The only weakness is a lack of English translations, but if you don't mind choosing a song without knowing the meaning it's excellent.
