I: The liturgy and its development--1. Definition and terminology--2. The structure of the liturgy--3. Origin and development to c. 600--4. The development after 600--II: General aspects of the chant--1. The texts--2. The notation--3. The tonality--4. Methods and forms of psalmody--III: Stylistic analysis--1. The liturgical recitative--2. The free compositions: general aspects--3. The free compositions according to type--4. Ambrosian chant / by Roy Jesson--5. The Old-Roman chant / by Robert J. Snow--Conclusion: Prolegomena to a history of Gregorian style