The following is from an email I just sent to my schola:
I highly recommend this website to work on your intervals: http://classic.musictheory.net/90. Uncheck anything higher than a perfect 5th, you simply don't need it for chant. Make sure you also click the direction button every so often so that the intervals will play down as well as up.
If you'd like to work on your modes as well, this is very helpful: http://classic.musictheory.net/91. Uncheck the major and minor scales and the Locrian mode. Also, keep in mind that Aeolian is the same as a natural minor scale and Ionian is the same as a major scale.
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