A very nice item.
The "German Singers' Association" might not sound like a particularly significant or impressive group, but this 75-year celebration was clearly quite a major affair, what with Hitler himself being present as well as diverse groups from the SA, SS, RAD and even the miners' guild. Also note the massive DRL/NSRL banner/column seen in the background of the photo with the SS men standing in front of the podium.
The Gau Nordmark clearly refers to a North German regional division of the Deutscher Sängerbund, and the one of which the album's apparent former owner, Ms. Martha Dolze from Lübeck, was a member.
Bravo, Andreas, thanks.