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.
