Ok, I'm not quit sure which combination of tags MuvUnder does to find the covers. If it's Artist + Album Name OR Artist + Album Name + Title OR Album Artist + Title but whichever the combination, the program (and all other cover program for that matter) always fail to find covers whenever a title have extra words like "featuring" and/or it contains parentheses/brackets like in john doe - mary (doe rmx).
One of the big hurdle in cover art programs finding proper covers for most of a collection depends on tags; any little e, or a, missing here and there can throw the program off. Now, there are a few genre of music which are hard to find covers automatically for because of the extras that are writen on the tags and also because Amazon and others write the name on their site differently: Hip-Hop, R&B, Reggae and Dance (sub genre...house, techno, jungle, etc...). As you can notice, most Hip-Hop and R&b songs have a "featuring" artist and 90% of Dance music are "Remix". These words are often writen fully or have a series of abbreviation like "feat.", "featuring", "ft.", "remix", "rmx", etc... and just because of these add up in the end of the title of a track, throws the matching off.
<Bob Sinclar - World Hold On> is easy to find but <Bob Sinclar - World Hold On (Benny Bros Rmx)> is not, however all the program needs to read is <Bob Sinclar - World Hold On> ignoring the parentheses. Same for <Jay-Z - Swagga Like Us> that's easy but once the program bumps into <Jay-Z feat. T.I., Lil' Wayne and Kanye West - Swagga Like Us (Rmx)> it doesn't find the cover, when actually it's the same song from the same album.
So, if there was a way to add a feature where the user could set a series of filtering/macro by telling the program to ignore certain parts of the tags then the level of return for these noted genres would be higher, extremely higher for Dance music. That way, the program would have the bare artist and title to look for. <Jay-Z feat. T.I., Lil' Wayne and Kanye West - Swagga Like Us (Rmx)> would become <Jay-Z - Swagga Like Us> once the user set a filter to ignore parentheses, brackets and the words: Feat, Featuring, Ft., Rmx, remix, mix, etc...