I was thinking of doing this with my answering machine, simply put the '9' MP3 at the beginning or end of my message so that if my wife isn't in and I forget/lo

I was thinking of doing this with my answering machine, simply put the '9' MP3 at the beginning or end of my message so that if my wife isn't in and I forget/lose my keys that I can still get in the building. Although it's a little redundant as I know so many people in the building that I'd probably be let in before the voicemail played the right tone. Plus my in-laws aren't a far walk for me to crash on their spare bed or pick up my spare set of keys. However, I basically just want to do it to see if it works.