Whether it was production, sound quality, glitches, background noise... I know when I listen to 'Beautiful' by Christina that at times you can hear the sound from her earphones on quieter moments of the song. In 'You Had Me' by Joss Stone there's a moment you can hear her bangles on her arm as she's moving. I also find my ears bleed a little during 'Bitch, I'm Madonna' when the "I just wanna have fun tonight" part comes in as it sounds much louder than the rest of the vocal track. I found this online: She forgets the lyrics to an entire chorus, but ad libs something instead. The album went on to win a grammy. There must be lots of this type of stuff right? Any other examples?