ITunes :: Merge 2 Apple Accounts?

Recently when trying managing my AppleID account, I was asked to make my appleID the same as my email. When I tried to do this, I was then told that an appleID by that name already existed. So I then attempted to login using my email address as my appleID. It was then that I realized that I have two separate appleIDs. One I have had for years, and has tons of music associated with it, the other I must have created in the last year when updating my iPhone software version. I have no idea how much of what is associated with the new one, but I think the only way I could find out would be to format my phone and start again. This sounds like a terrible test to conduct on myself.how one can merge two separate appleID accounts