님을 위한 노래 / 마음 is an album by 오정선 that was released in 1978 on SRB Records. The genre for this is K-pop, but it carries elements from some other genres, most noticeably enka, rock, and folk/country.
This album is very slow and downtempo. The melodies, her vocals, and the vibe of the album sounds melancholic or / emotional. Slow drums, slow vocals, and lots of slow bass, guitar, and strings helping build the feel. Some songs do pick up in tempo and/or sound happier than the rest of the album, not all of it sounds sad.
This is a great album, listen to it here