The correct answer to this open question is the following.
What makes the song "I’m Sittin’ on Top of the World" by Les Paul and Mary Williams so unique for its time is the high pitched sound Les Paul included in the song. Indeed the sound of the guitar seems to be artificial. The recording technology he used in 1953 was amazing. That is why "I’m Sittin’ on Top of the World" is a song considered to be a technological wonder. The overdubbing played a major role in the sound of the song.
Les Paul (1915-2009) was a famous blues musician, considered a guitar innovator due to its creative guitars and sounds.