A MP3-DVD is a DVD-disc with MP3-files burned as a regular data-DVD.
To try out the MP3-DVD compatibility of the NorthQ 7100, I burned a DVD with the same structure as the CD I burned to test MP3-compatibility. Then I inserted it in the DVD-player and hoped for the best.
It turned out that the NorthQ had no problems with this disc! It played the MP3 songs and everything behaved exactly as in the MP3-compatibility tests!