You can watch and listen to the cover in question here, and you really do need to watch it. It's not just a violin version of the Super Mario soundtrack - Teppei goes a step further and integrates sound effects from jumping, swimming, grabbing power-ups and more in real-time. He also covers tunes from several levels and sequences, not just the first level. Yet Teppei never breaks the tempo of the background music itself, making for a truly dynamic and stunning compilation.
Teppei originally posted this cover back in April 15, but it didn't get picked up by English social media until this week. After seeing it, Keighley promptly reached out to Teppei on Twitter, suggesting that "we need to book this guy for Summer Game Fest stat." Keighley's latest tweet confirms that he's at least gotten in touch with the violinist, and while there's no guarantee an appearance will be arranged - especially with geographical boundaries and the state of the world - we may actually see or hear Teppei in one of the SGF events still to come.
If you want to see more of Teppei's work right this instant, you can find several other amazing covers on his YouTube channel, including F-ZERO and Sim City covers. His Kirby cover is also to die for. If we do see any Summer Game Fest announcements from Nintendo, I sincerely hope Teppei is involved.
Nintendo certainly has some games to announce this summer. Just recently, the company dropped a trailer for Paper Mario: The Origami King out of absolutely nowhere, and it's rumored to be preparing Pikmin 3 and other remasters for reveal.