This commemorative decoration was attached to the wall of one of the buildings adjacent to the Marienkirche, apparently put up in 1935. Being a fan of Johann Sebastian Bach, I recognized the name of Buxtehude on the bottom, who was another well known virtuoso organist and a predecessor of Bach.
The text on it reads:
St. Marien Werkhaus
Here lived the master Organists:
Franz Tunder 1651-1667
Dietrich Buxtehude 1668-1707
Buxtehude was here