This is The Fox by Ylvis redone on Minecraft using note blocks... with a small twist!
If you haven't heard about it, you can check out the original here: www.youtube.com/watch?v=jofNR_WkoCE

This video was recorded in completely vanilla Minecraft. I made a custom resource pack to reskin wolves into foxes and add part of The Fox into a random sound file. I then used command blocks with /setblock, /summon and /playsound commands to do the stuff you can see in the video. Some tricks I used were spawning the animals with resistance 10 so that they don't die by fall damage and spawning some foxes (wolves) riding invisible bats so they can fly.

I used the Minecraft Note Block studio to make the note block song. You can find it here: www.minecraftforum.net/topic/136749-minecraft-note-block-studio-200000-downloads/

If anyone wants to make use of the fox textures, here's a link to the resource pack I used (minus the custom burp.ogg sound which I replaced with the chorus of The Fox): www.mediafire.com/download/jc3zw1kat1qt228/fox.zip

Thanks for watching :D