What's the range on this Melodica?
 

YouTube - Augustus Pablo - Jah Light (melodica)

I want to buy one that sounds like his, but I don't know the first thing about telling what range a sound is.

The one the guy is playing definitely looks like a Hohner HM-32 (32-key) melodica.

The HM-32 will play both the soprano and alto tonal ranges, which is all you need.

You're probably talking about $100 U.S. dollars, if you order one online.

If you've got more money to spend than that, you can pick up a Hohner HM-36 (36-key) professional model, that will play a 3-octave range and a tonal range from F through E.

I'd say you're looking at another $80 dollars for the HM-36.