Chipettes real voice?? (Bad Romance & S.O.S. at 70% speed)

I've always wondered what speed to play a song at to get the voice of the Chipettes. For the Chipmunks it's an easy 0.5x, however when a song with the Chipettes is set to that speed, the voice is clearly too low. After some finagling, I'm thinking that the correct speed here (at least for the live action movies) is 0.7x. Sounds about right, don't you think? Let me know if it should be faster or slower.