This song has been difficult to find as it was not included on the Legend soundtrack (although some of this melody can be heard at the end of the song, "Loved By The Sun", as it fades out.).
This version was included on the album Booster part 2 and titled "Beyond the Cottage and the Lake".

There also was another bootleg of TD music called Electronic Orgy that has a 7 minute portion of the Unicorn Theme on it. The ending of the song is more developed and there is no voice over of Oona. This can be heard here    • Ridley Scott Legend OST - The Unicorn...  

A nice piano version of this song.
   • Legend Theme on Piano - Tangerine Dream  .

The Directors Cut of Legend features a score by Jerry Goldsmith, which some people seem to prefer. But in my opinion, I think Tangerine Dream's music is a big part of what made this movie special. It made it seem surreal, like a dream. Jerry Goldsmith's score was more traditional and made the movie seem almost like a Disney film.

Legend was directed by Ridley Scott and released in 1985. It stars Tom Cruise and Mia Sara.

I will do an updated version of this video if Legend is ever released on 4k Ultra Blu Ray