WARNING - The BGM is MONO, the 3DS has some issues playing mono BGM's.
It plays the song normally on the left channel, but plays either nothing, the bgm before or noise on the right channel.
The only way I found was working, was to set the output to mono in the 3DS settings. :/

"The King for Another Day Tournament is a 2019 channel event and the sequel to 2018's King for a Day Tournament. Like its predecessor, it sees characters battling it out in an elimination bracket determined by the fanbase's votes, with the winner of the tournament receiving their own special day to take over the SiIvaGunner channel, and the runner-up receiving a fusion collab."

Source: https://youtu.be/L96geMVswxE?list=PLL0CQjrcN8D08kd1Cmr-ncqfajomFK98P

Info: https://siivagunner.fandom.com/wiki/King_for_Another_Day_Tournament

Lo-Fi 8-Bit High Quality Chill Beats to Train and Relax To - SiIvaGunner: King for Another Day