If you think about it, While Doing isn't really that complicated or dynamic a song - it's basically a simple melody put on top of a looped instrumental with a pretty piano line. What makes it special is that, like a few other fantastic songs this year, the simplicity was done on purpose - to make the singer's voice stand out. And boy does Hwanhee's voice stand out.
The song was made to be carried by vocals - the beauty of the song comes out in how Hwanhee wants to sing it, and how he wants his voice to sound. For someone with vocal technique and actual vocals as good as Hwanhee, it's no surprise that the song came out fantastic. And when I say fantastic I mean I'malmostspeechlessbecausehisvoiceisgorgeousandifiwasn'tawriteriwouldreallybespeechless.
Have you HEARD this live? I'm dying just thinking about it. And apparently, he was sick during that time. The horrid outfits he had during promo, which can only be described as vile, throat-eating things, have been forgiven. I choose not to remember them, for my sanity.