@troux, @Lugia
Decidedly, since the bids rise easily here, I will claim in my turn that, in the Western world, the 'drone' was born with the plainsong, in the sacred music, in the Middle Ages.-- Sweelinck
But then, you have to take into account that Plainchant descends directly from the Grecian Modes. And with those, musicology isn't 100% certain of the lineage. Then you go backwards from there, across other Eastern Mediterranean region people, whose tunings and scales were somewhat more complex...and still are. But also, taking Alexander's conquest travels into account, we're probably looking at some sort of "polyglot approach" to encountered scalar, etc techniques, and those certainly got mixed in with the rest of the goings-on in that area.
But MY big point is that, if you go back to the point where music as we currently know it originated, you're dealing with the Central Asian region, and that back around 5000-7000 BCE their musical elements migrated with various peoples into these different sonic cultures. And back then and back there, the drone was PARAMOUNT. Entire musical styles emerged, with the best known of them being the Mongolian and Tuvan cultures where the drone is also important to the generated harmonic pitches that result in throat singing, which is where I and others think this starts. Given that the harmonic series' first several partials fit Western tunings, it would also explain early instruments that seem to be "close" to present-day tuning, so that these could match up with the harmonic pitches. It's also the source for Tibetan ceremonial music, the drone aspects of Persian and Northern Indian music, and on and on.