Heard some amazing Turkish classical music this evening.. the modes used (phrygian, etc) create a very sensuous effect, and clearly there is a lot of melismatic voice over a drone bass. Definitely melody and accompaniment. Two voices? no, I think the drone simply 'amplifies' the voice.. it resonates sympathetically.. (interestingly we were talking about sympathetic magic and the Lescaux caves this afternoon...). The distinction between sympathy and conflict needs more thinking about!