Audio problem: When Troy and Gabriella are singing "Everyday," Troy sings with his microphone away from his mouth numerous times during the scene, yet he is still heard just as well, and not at a lower level, like he should be. (Within the context of the film, this is sung live on stage and is not implied to be pre-recorded.)
Audio problem: Near the end of the song 'Everyday' when everyone in the circle has moved forward to the centre of the stage, Troy turns back to the audience singing 'everyday' and you can hear Gabriella's voice but her mouth is not moving at all.
Audio problem: During 'You Are The Music In Me', when Troy lifts Gabriella off the piano, Gabriella mouths the words 'Oh yeah' then three seconds later her voice is heard without her lips moving.
Answer: It is just a coincidence. Corbin's character is all about sports and feels that Ryan is not in the same league when it comes to baseball (pardon the pun). Ryan, on the other hand, wants to prove that dancing takes just as much athleticism and dedication as sports therefore the game and song are a showdown between two cliques you generally find in high school, the athletes and the drama club.