Why Christine?

Out of all of the beautiful women of the Opera, why does Erik fall in love with Christine? OK, I know he gave her singing lessons for 3 months, angel of music, etc., but why did he give her lessons in the first place? Was he already in love with her? Or did he fall in love with her as time passed on? :idea:Maybe he felt somewhat connected to her! Her father's dead, she only works at the Opera because she has to, and maybe, before the Angel of music helped her, felt a little trapped in a world of the past! Maybe he thought he could win her trust, and only began to love her after she noticed Raoul at the opera (before the gala)!
Anyone else got an idea?

He fell in love with her voice over time he fell in love with her. so the book says..... she truly loved Raoul.