SOUNDHAX IS ONLY COMPATIBLE WITH USA FOR NOW, EUR AND JPN SOON!
IT DOES NOT WORK ON o3DS's!
Go
here and get the Homebrew Starter Kit. (Extract it to the root of your SD card).
Go
here and get your OTHERAPP payload (Make sure its for your current Version and Region). Rename the .bin to "otherapp.bin".
Go
here and get the exploitable .m4a sound file. (USA .m4a only, once EUR and JPN is available ill update the thread)
Put the OTHERAPP payload and .m4a on the root of your SD card. Make sure you also extracted the Starter Kit to the root of your SD card aswell.
Boot up Nintendo 3DS Sound, Wait a bit for it all to load the SD card, Open "/SDCARD", Open the "<3 Nedwill 2016", And enjoy.
(If it crashes, confirm the OTHERAPP payload is for your system version and region. Keep repeating the usage step until it works, It will take a few tries).
Done!
It's that easy! 2 files and load the m4a. Easy!
Credit: Nedwill (Soundhax), Smea (OTHERAPP payloads).
Github Repo