The Singing Sand Dunes is where Dunestock is held, so for some good directions to the place, visit their website:

http://www.dunestock.net.qa/directions.html

You don't have to have a 4x4 to get there as long as you don't try to drive up the dunes. The area around them is hard, flat and slightly rocky.

The only problem getting there now is the darn road construction.