Roger in Sheffield:
Great clicky - I've bookmarked it for my S.O. to see.
But noone (including the kazoo site) has mentioned the true "primitive" kazoo.
When I'uz a little pup, we used to just wrap a piece of mama's waxed paper across a pocket comb and make music 'till they throwed us outa the house.

The best comb to use is the old standby "Ace" hard rubber.
For some reason them modern plastic 'uns aint got the same tone.
You can get the old "Ace" at some of the Walgreens stores, and the come in a version with all the fine teet (for tenors) or with half fine and half coarse teeth - use the coarse end for the baritone and base notes.
I don't recollect hearing about a "tuning spine," but the ol' comb has a purty sturdy backbone, and you can use it to purty up yerself when the girls all come fallin' all over ya after they've heard yer purty music.

John