This PDF document has the definitions of Subject Matter, Theme, and Symbolism and aids in a classroom discussion about the relationships between the three. Included are some examples of visual aids.
I've related this assignment to music because I often play music/music videos as a part of the class discussion. The first video or song I use as an example and the second I use as a form of competition. The group that can explain the Subject Matter (lines from the song), Symbolism (what they mean), and Theme (overall idea) wins a prize for the day.
Pink Floyd - Another Brick in the Wall (Music Video) [Class Discussion]
Potential Songs for the Group Assignment
Chicago - 25 or 6 to 4
The Police - Every Breath You Take
Blues Traveler - Hook
REM - The One I Love
Lyrics for each of these songs may be found online and...with the help of Spotify I was able to play many of the songs I needed.