Ayu's ear-things

[Kaiousei]

This is prolly a stupid question, but I was just wondering cuz i was just watching her concerts...what exactly do the earpieces tell during her performance. besides the fact that they cue her..i was wondering if they help her sing in harmony better, do they have her singing so she wont forget her words or something???

i was comparing times when she wears them and times she is not (like in her earlier performances) and she seems to sing better.

...just wondering