Enjoy the oldest surviving organ piece! It's from Robertsbridge Codex which was compiled in the 14th century (ca. 1360), from the time of Boccacio and Decameron. This music is of Italian origin but preserved in the British Library.
One of the most characteristic pieces from this manuscript is Estampie - a dance with many paralel fifths with several stanzas (puncti) each of which has two different endings (overt and clos).
It's so fascinating to hear the sounds from almost 700 years ago, from the times when the Black Death roamed Europe. Watch the video of how it sounds here. This score has 3 pages for manuals only with complete fingering and registration suggestion.