That's was excellent. I'm not really sure what technique he is using to get that whistle sound, but he knows how to control it perfectly. Amazing!
Below is a song by Norwegian singer/songwriter Marit Larsen, who is probably best known in Norway and Germany. I think it was in about 2010 that it became a #1 in Germany for several weeks.
https://youtu.be/Qje3U2eRuQ0There's a lot of geo-blocking that takes place with her label; many of her music videos are blocked. If that video was blocked, here's a live acoustic that might work:
https://youtu.be/KiQI2px4kSwAnother video on Vimeo:
https://vimeo.com/32140593I had never heard of her until a musician in Europe mentioned her to me a couple years ago. Her parents are both musicians; her father plays cello in the Oslo Philharmonic and her mother teaches piano. She recently announced at her Facebook page that she wants to release her next album in April on her own small label (without geo blocks).
Another song of hers called "Under the Surface":
https://youtu.be/9gyv4mb6zYY