I then went to The White Album- but it's not a song.....
IMHO an album can be a song when it has a cohesive theme that is supported by the several pieces of music. Much the same way the libretto of an opera is supported by the several pieces of music in it.
Pink Floyd's The Wall is a clear example of an album that constitutes a song because each piece expresses a unique portion of the overall narrative of the album. The several pieces of music can be heard and enjoyed separately but to get the full impression of the artistic message the entire album should be heard as a song at one time.