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In page Jan Blahoslav:

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Blahoslav was the editor of the 1561 Czech-language hymnal of the Unity, a hymnal which was reprinted and revised at least 10 times over the next 50 years.[1] His Muzika (1558) -- a "theoretical instruction book for the singing of hymns" -- has been called "the first book in Czech presenting the theory of music and singing."[2]