Message Tone Changing

This question has probably been asked before, but after using the search feature I came up empty handed sadly.

I know how to get a tone from my PC, onto the phone. I have setup a custom ringtone myself, which wasn't difficult. Put the file on my phone, and assigned the ringtone. My issue is when I search for messagetone, I doesn't find the tone I want to use.

I have moved the file from the memory card to the phone itself, and it still is not showing up. Does the bitrate have to be different for a messagetone?

Any help would be appreciated.