[whatkind]

I know, i'm using a romanized name when the official En name is not found.
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It's not the official name, just like a title of homepage.
Nissho is an abbreviation of Nihon Gasshou Kyoukai (日本合唱協会). >>日唱

NISSHO CHORUS could be more official if you'd like to get one.
See official site below.
http://www.nissho-chorus.com/ copyright©2014 NISSHO CHORUS all rights reserved.

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Why I didn't use NISSHO CHORUS is that NISSHO is an abbreviation of Jp name.