The hasConductor check for Classical catches too many non-classical, such as this song by REM - http://musicbrainz.org/recording/79f7dc21-3ccf-40eb-abb4-30ef41ca999b. We need to be more careful when identifying Classical as it can lead to unexpected artists for users.
Perhaps have some negative checks first, i.e if work is of type 'Song' then not classical.
Perhaps should consider all songs in grouping, i.e we need all to be classical not just just some.
Maybe weight according to classical/nonclassical markers and only make classical if classical outweighs nonclassical