Praeludium in D Major, BuxWV 139, Dietrich Buxtehude 

A wonderful example of the North German organ school and Stylus Phantasticus, this piece is a 7-part fantasy, including 2 sections which seem to call for alternating between registers, a fugue, and a few short interludes before the grand finale.
Performed as a postlude to a Sunday service by organist Dan Campolieta and captured live on a long shot camera at National Presbyterian Church in Washington, DC on the 1970 Aeolian-Skinner op. 1456.
(apologies for a couple times the video/audio feed breaks up for a second)