The rapper apparently posted When I See It two weeks ago but it only went live on Monday.
It features a mellow West singing of his recollections driving on a Los Angeles highway.
The release immediately sparked speculation on social media that the song will appear on the next West album, which he says will be called Swish.
West himself has played down expectations of an imminent album, recently telling Vanity Fair magazine it was like a complicated painting and could take him another year.
The star, who has likened himself to Michelangelo with his diverse talents, last released an album in 2013, but has remained constantly in the public eye ever since.
In recent months, the husband of reality television star Kim Kardashian scheduled a surprise show at New York Fashion Week and announced, with an uncertain degree of seriousness, that he will run for president in 2020.
- AP