While it’s nothing too special, it’s interesting how the user pulled it off. He doesn’t go into the complete details, but here is what he said on YouTube:
I got a 3DS yesterday, and I was busy messing around with OoT’s Ocarina. After applying the necessary supplies (iPod dock for larger speakers/sound, Nyko pedal for mic support, etc.), I was able to FC something using the game’s Ocarina. lolwin
It really trivializes games that allow singing, but still it’s pretty cool. Next up, someone subs in Ocarina of Time 3D for a guitar in Guitar Hero.