there is no difference between lipsynching and performances with very loud backtrack.
I think people who use performances with very loud backtrack to prove that their faves sing live are looking at this on a very shallow level, they just don't want to have the lipsynch label linked to their faves but they are forgetting that you are supposed to HEAR the LIVE vocals in live performances. It's a straw man argument and a cope. who cares if an idol's mic is on when all we can hear is the pre-recorded backtrack and not whatever feed the open mic is sending?
I remember a while ago there was a thread about lipsynching and someone posted a performance to show off their faves' live singing and when people pointed out that you can't hear the supposed live singing under all the backtrack, the person insisted that it doesn't matter whether you hear it or not and that all that matters is the knowledge that their mics were on. Excuse my language, but what the fuck? that's bullshit, mumbling inaudibly behind a loud backtrack is anything but live singing. in my book it is as bad as lipsynching, in both cases the final product that we are listening to is a studio recording.
live performances for me are when you can hear the live vocals clearly beyond any shadow of doubt, like this
or this
ps: there is a part in Mirotic where Junsu says "can't you go down on me" 





