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Maybe 'Blues Clues'. I'm not sure about the other stuff but it had a live-action white guy, and a cartoon background.
Blue's Clues also had the host Steve jump into photos and books and stuff, and he did leave the show to play music so that could be the deal about the music video thing. But I don't know about the whole finger-curling thing; that makes me think it's not Blue's Clues because it was my favorite show and I remember nothing of the sort.
"Don't cry because it's over, cry because it happened."
Bear with me. You know that kids show with real people (and possibly cartoon backgrounds like Lazytown), where the main guy was white with black hair (I think) and he would do this thing where he put his pointer and middle finger beside eachother and curl down the other fingers on each hand. And then use those two to make a plus sign. And then he would teleport into a TV or something. There was a vine about what it would be like today where the guy goes into a music video. Help, please.