This might be an oft invented thread, but I reinvented these for my Musician's Anonymous page, which you can find at http://sondahl.com

You may be a musician if...

The callouses on your fingers are thick enough to handle hot dishes from the oven without a hot pad...

You tell your spouse you're going out to spend the evening playing music with some friends, and then actually do it.

You have too many instruments to carry all at once.

You can "rationally" explain to your spouse why you needed that third guitar.

It bothers you that "Waltzing Mathilda" isn't a waltz.

Feel free to add your own qualifiers...
Brad Sondahl