As we continue to dig deeper into Legend of Zelda: Breath of the Wild, we're beginning to see the game does have some similarities to past titles. In this video shared by Rouliboudin, we learn that the Song of Time is playing in the background music very slowly.
It's a little confusing because the Song of Time playing at the beginning of the video is from Majora's Mask I believe (Zora Guitar) and used as a point of reference for what you will hear in the video after.
The more I see on this game the more excited I am to play it! 2017 can't come soon enough!