Via m-trends.org comes news that Nokia have created the Nokia Music Mixer as a promotion for its XpressMusic branding. The site allows you to remix your own ringtones via a web based user interface. The custom ringtone, in AAC format, can then be downloaded to your phone using a link sent via SMS to your phone as well shared with other users of the site. 

Of course remixing software is also available for some Symbian Phones. The most notable example of this is FirePlayer as seen on the Orange network in the UK. Still Music Mixer is a good promotional item and should give you a chance to create a custom ringtone to replace the Nokia tune .