I found those two pieces for mandolin and church organ recently. Both pieces are taken from a recording with religious music which was recorded in the 1980s by Benny Ludemann (mandolin) and Klass Jan Mulder (oragn).
Benny Ludemann is a mandolin and guitar player from the Netherlands. He has made many appearances in radio and TV. He is teaching mandolin andguitar and has made a big contribution to the mandolin orchestra association of the Netherlands NVvMO
The mandolin part ist played with tremolo. Pleas enjoy this rare combination of mandolin and organ.
Klaas Jan Mulder (orgel) en Benny Ludemann (mandoline) – Scheepke onder Jezus hoede
Klaas Jan Mulder (orgel) en Benny Ludemann (mandoline) – Ik wens voor Hem te leven
I have found one other video with Benny Ludemann from a TV show, Benny Ludemann plays the guitar in a piece named 24 Roses.
24 rozen – Benny Luemann
You can find a note about Benny Ludemann in German here: http://www.mandolinen-orchester-koslar.de/Texte/jury.htm