The key one that got me into overtones is Sunn O))). They perhaps don't have a huge direct overtone presence on first listen, but there's something about the scale of the sound they make that touches on the kind of ritual sublime that for me functions in the same way as a lot of overtone presentation. The vocalist they often use, Attila Csihar has an incredible range that includes overtones, which led me down that route. I think as well there is something in the interaction of tone in drone music that keys in to overtones - because the structure is often so simple it becomes possible to appreciate tone itself rather than necessarily just melody. The metal element is purely through investigation of vocals other than standard western singing and exploration of what the voice can do - I found Karygaa fairly easy to grasp the basics of, possibly due to being an extreme vocalist - there did seem to be some parallels in use of the throat.

Well, the drone is very important for overtone music, since there must be a fundamental tone. With a steady fundamental, a drone, you get the harmonic series you can build overtone melodies on that will always sound good.

http://alonetone.com/danibal/tracks/heavyploing here's an old track i did on jewsharp. it's done with a simple distortion wich makes the overtones needle sharp. be careful with the volume though. ;)