- Albums have songs.
- Songs have name and durations.
- An album has a band - the band that created the album.
- A band has a name and keeps a reference to similar bands.
class Album { int year; List<Song> songs; AlbumGenre genre; String name; Band band; }
class Song { int minutes; int seconds; String name; }
class Band { String name; List<Band> similarBands; }