Obviously there's not usually going to be "indian instruments or singing". Goa Trance is supposed to be the electronic cyber-shaman dance music.
If there was sitars, that kills the atmosphere IMO.
There's lots of ethnic melodies, appregios, OHM basslines in Goa Trance.
Goa Trance always reminds me of spirituality and the dance of shiva, I dunno it's all there man. Feel it = )