Actually I've always have this idea but I can't use it anyway.
The guy is out with the girl and a friend will be ready at home.
The guy will find a suitable time (no matter where also can), then secretly msg the friend a signal.
The friend will call the girl and when she answers, the friend will play "a mid-summer night's dream".
Initially the girl will sure feel funny then she will find it ridiculus and she'll tell you about the music

.
Then you'll say that that's your friend helping you, and that's the time you take out the ring.