I share with you my transcription of the Missa XI Orbis Factor in modern notation.

For harmonization I have been guided by the one used in the NOH.

This arrangements are intended for beginning or amateur musicians.

When accompanying the melody use the chords only in the fundamental position or in the first inversion (never in the second).

Make the change from one chord to another as smooth as possible, and keep common notes tied together as much as possible.

You can find more transcripts on my page: https://sites.google.com/site/gregorianicantus