If with the default options SongKong is incorrectly marking some releases as Classical when they should not be we can prevent this permanently by modifying the not_classical_release.txt file. This can be found with the other preferences files such as general.properties and license.properties.
Please note the active preferences files are not within the program installation folder, the files are copied from there the first time SongKong is started to a user configuration folder. For example on Windows this folder is C:\Users\username\AppData\Roaming\SongKong, from then on SongKong uses the files in the user configuration folder.
Here is the contents of the start of the file:
9a4929eb-6ec5-4a9c-8242-2377035fe05d = Sgt. Pepper's Lonely Hearts Club Band 486c04ad-f06d-456f-86fe-9d3e74d2a697 = Welcome to the Pleasuredome 0d13ce42-87bc-492b-9ccb-95658a06cc39 = Swing When You’re Winning d304d0ae-4937-30a9-9ea7-656a8d92860b = Intensive Care d01c2f7c-9d7b-4e74-b807-8290ce9c8523 = Tales of Us 882bcb9c-0b1f-42f1-9a01-3e74cdec6d46 = For the Good Times: A Tribute to Ray Price
Each line is of the form MusicBrainzReleaseId = Release Title and you can simply add more lines and then restart SongKong and that will prevent it marking songs matched to this album as classical in the future.
When a song is matched to a MusicBrainz release the MusicBrainzReleaseId is stored in the MB Release Id field
And if you view the release in the MusicBrainz database itself you can see the Id in the url of the webpage