If you have Rdio IDs for your songs (or IDs from any other streaming service that's part of Project Rosetta Stone), then there's a much simpler way:
Rather than putting artist and song names in your taste profile, and requiring us to try to string-match them to the Echo Nest world, just put the Rdio foreign IDs. To record a track play, for example, send us just a track_id of rdio-US:track:tXXXXXX instead of artist and song titles.
And similarly, you can use these Rdio foreign track (or artist) IDs anywhere else you're using the API rather than the Echo Nest IDs. So you shouldn't have to maintain any mapping on your end at all.