As anime, manga, tokusatsu, TV dramas, and the like became more popular, the magazine became more of a digest or anthology of stories, theme songs, and pictures from these series.
Since all of them were drawing from the same sources, the Asahi Sonorama and its rivals would often release sonosheets and vinyl records at the same time.
Asahi Sonorama (the company) began to move into the vinyl record market at this time.
Due to the flooding of the market with similar goods, many companies began going under in the 1970s because they couldn't maintain their production levels and still make a profit.
Unfortunately, the market for picture books with included records disappeared quickly in the 1980s, so they refocused their attention on the regular publishing business.