Hermann Schroeder (1904-1984) ranks among the major German organ composers of the 20th century, being an excellent organist himself. Many of his more than 100 organ works deal with themes of the Gregorian chorale. The chorale's modal diatonicism which is freer and different than the later major-minor tonality establishes a perfect symbiosis with the free tonality of the contemporary composer. In the five-movement chorale partita, the more than 1,000 years old Mixolydian Whitsun Sequence of Hrabanus Maurus (9th century) is used in an imaginative and formally varied way: as a virtuoso toccata, in the second movement 'ostinato' as a strict trio setting over a seven-bar ostinato in the pedal, as a capriciously playful 'bicinium', and as a meditative, harmonically appealing 'arioso'. The fifth movement (fantasia ricercare) displays brilliant full-handed chords and virtuoso passages as well as a fugato in the middle section. A rewarding concert piece for Whitsun, with an excellent possibilit y of virtuoso interpretation and colourful registration.