Just found another set of useful organ pieces on carols, these by J. de Montber - very playable.

any biography about J. de Montber ? can't find any information about him !

Are any of Reger's shorter and simpler organ pieces suitable for Advent, I wonder? Some of his chorale preludes are no more than a page long, and can be played by any adequate organist at sight without too many mishaps. But I can't recall whether they include Advent-related works.

Where are these on your site?

Broken link?? It hasn't worked for me:

http://www.frogmusic.com/advent--christmas-organ.html

"Three books of music in PDF now in the public domain for legal printing and sharing:

The Advent & Christmas Cantantibus Organis of early organ music, much chant based.
Fantasy on Well-known Christmas Tunes
Novello Volume 8"