if I was going for a modeling job in the games industry my reel would be about 3 minutes my models would be fully textured and rigged showing them I am a man of many talents and that I could do the work of two people, prehaps three (modeler, texturer and animator) thus increasing my chances of get the job, as for contents, well if dont like something it wont go in, only show your best and I would try show a broad spectrum of models from character (male and female, human and non-human), structure (lamp posts to buildings), vehicles (horse drawn wagon to futuristic vehicle)

or

if I was going for a modeling job and thats all I wanted to do then my reel would reflect that and have the basic models nothing else, my content would still be the same.

oh and as for music I wouldn't bother as everybody has different tastes in music, unless its an animated scene that requires music.

You might already know all of this you are doing a course, this is how I would go about doing mine.

Dae