I really appreciate it that you've been reacting to both K-Pop and J-Pop. :) Have you checked out Yoasobi's YORUNIKAKERU English ver.? It's absolutely incredible! :D
Here is a song to help you along on your musical journey. "Misty Mountains" is the song by Peter Hollans (high tone singer) featuring Tim Faust, (low bass singer). They both work in Acapella groups. You will hear as one vocal coach, reactor said ,"That's the lowest note I've heard come out of any human". Misty mountains is from the "Hobbit" movie so they are in costume. Enjoy!