D. Buxtehude - Chorale Prelude, BuxWV 199 - T. Koopman (live recording)
Dieterich Buxtehude’s was an important composer from the mid-Baroque period. His works influenced greatly the music of J.S. Bach. His organ works mostly focus on the use chorales. Nineteen organ preludes are the backbone of his compositional output and are composed in the stylus phantasticus style, which was of huge influence to Bach.
Buxtehude also wrote 30 chorale preludes for organ. A chorale prelude is a liturgical composition which highlights the use of a chorale tune. It first became an independent genre during the Baroque era in Germany. Buxtehude was responsible for establishing it as a genre, which then went on to be developed by J.S. Bach.
The style in which Buxtehude ornaments the chorale is very similar to how a vocalist would do so during the time. The accompaniment is simple, almost like realized continuo, with small amounts of imitation and contrapuntal ideas used during interludes between the chorale phrases. The chorale is so highly embellished in places to the point that the original is almost unrecognizable at times.
Source[]
http://highered.mcgraw-hill.com/sites/dl/free/0073137944/829904/Chapter22.pdf
http://www.dacapo-records.dk/en/recording-organ-works-vol--1.aspx