There's a great show on SBS(Seoul Broadcasting System) called "Fantastic Duo's". The way it works is you download a region-locked app. from the Korean marketplace on iOS or Android. After you download it there are multiple options but one of them is "Sing With Star" and you pick the one that says "Now Apply" or something like that and you sing along with the star in the video that pops up. It's called Smart Karaoke and cues you accordingly in Korean text on the screen.
For those who sing well enough on the videos and have an intriguing video as well they are chosen to appear on the show with the star. After that the list gets whittled down from the 5 or 3 chosen to appear on the "Fantastic Duo" show down to one and MAN, there are some great voices singing along with the star. I strongly suggest watching some of these performances, they are stellar. Some performances are so good after hearing the regular song I would rather buy this rendition than the official song or at least buying a live performance from the artist instead. Hearing Ailee perform "Heaven" live with her partner then hearing the m/v, I would rather buy the "live" version with(full) or without partner as it doesn't sound so processed. I might feel the same with IU's song, I'll wait to listen to it via the m/v.
I haven't watched the show in its entirety since I don't get SBS but if I could get that stream here in the US I would grab it in a heartbeat to watch this show and others. I've mainly seen it from clips that have been uploaded from SBS online.

p.s. I'm not positive if they're chosen deliberately or randomly.