Unexplained Audio Caught on Tape

Unexplained Audio Caught on Tape
This video was taken inside a cathedral,listen carefully.
I went to visit this cathedral and there was only like 6 people inside, One older lady praying the rosary,The whole time I was filming, I can hear her Singing. I never noticed until i went outside to changed my batteries from my camera, Something else took over the audio, In the video you can hear just for couple minutes her voice.
Than after that some creepy voice that took over the audio, I never noticed that until i heard the audio again and again. Is like a demonic ritual going on you can hear it very well.
I have no other words to explain how this happen, Is crazy and amazing recording audio caught on tape.
This Cathedral is in Leon Guanajuato Mexico.
Oratorio San Felipe Neri