Diamanda Galas (that's gaLAS) is one scary woman, fierce and uncompromising in her approach to music and her choice of material. Her stuff is emphatically not easy-listenin', and it's difficult to know where to start when introducing her to people who've never heard her. But consider two brief outtakes from a 2004 radio interview (from Hellenic Public Radio, but no longer available in their online archive) as a jumping-off place: gales of laughter (0:26) and on blues and rembetika (1:54).
Now, if you dare, try something from La Serpenta Canta. And, if you survive the intensity of that, move on to Defixiones, Will and Testament, which is "dedicated to the forgotten and erased of the Armenian, Assyrian, and Anatolian Greek genocides which occurred between 1914 and 1923..."
Whew. But for my money, she's an amazing musician.