On this forum's host website (http://www.musicasacra.com/) if you scroll down on the right side, you will see a section of resources called "Teaching Aides." About 4/5 of the way down the list of resources, you will see, "'Textbook of Gregorian Chant' by Dom Sunol (1930)." If you open that PDF file and go to pages 40-45 of that book, you will find a series of solfege exercises and typical melodies for each of the eight modes.
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