I think most who know of Genzuki might have heard that he's learned a ton of instruments, but he also used to be in a band years ago. Rarely ever shows playing other instruments raw but here's an old drum clip of him fucking around.
https://www.bilibili.com/video/BV1mA411J79SHe is more known for his piano playing in Nijisanji. For a more well known fact but probably lesser known to those who don't watch Nijisanji JP, he has done mixing and/or backing music for over 50 covers/videos in Nijisanji, original Nijisanji songs for himself, his unit, and other units, and even stream BGM for himself and others.
Songs he's done mixing for
https://wikiwiki.jp/nijisanji/%E5%BC%A6%E6%9C%88%E8%97%A4%E5%A3%AB%E9%83%8E#genzuki_helpSongs he's composed lyrics for (some are shorts)
https://wikiwiki.jp/nijisanji/%E5%BC%A6%E6%9C%88%E8%97%A4%E5%A3%AB%E9%83%8E#made_songs 
