DDR: Musical Instrument Museum

This cover includes two stamps from the former German Democratic Republic (Deutsch Democratische Republik, DDR). They are from a set of 4 stamps issued in 1979 showing various important instruments in the Musical Instrument Museum in Leipzig. The present stamps show a lira da gamba and a German tenor trumpet. But on the cover, the organ-interest items are not the stamps, but the postmark and cachet. Included in these two black-toned images are two different organs in the museum.  I was not able to find a list of holdings at the museum. The organ in the postmark thus remains a mystery. The cachet, we are told, shows an Italian positiv from the 1500's. The stamps (Scott 2031 and 2034) and the postmark include 1979 dates. The museum began as a private endeavor in 1886. It was absorbed by the University of Leipzig in 1929 and has been under their aegis since.