When we heard news that there is no built in method of adding custom ringtones in WP7, we were shocked that such a crucial feature would be missing from the OS. It looks like there might be a way around this, according to the programming geniuses at XDA-Developers. Tucked away inside the OS, they found the undocumented capability to add a ringtone from an app, called ID_CAP_RINGTONE_ADD.
This means (hopefully) that apps will soon be available to add custom ringtones to WP7.
It also looks like you’ll be able to buy ringtones through the Marketplace, as described in Microsoft’s own documentation:
On Start, tap the arrow to go to the App list, then tap Marketplace .
Press the Search button.
Do one of the following:
To browse a variety of ringtones, type ringtones, then tap Enter .
To look for a more particular type of ringtone, type something more specific, like Halloween ringtones.