Aftanas etal reported on the relationship of theta and bliss in Sahaja style meditators in the paper "Human anterior and frontal midline theta and lower alpha reflect emotionally positive state and internalized attention."
Bliss was associated with increases in frontal theta in the range of 3.77-5.65 Hz for experienced meditators.
Sahaja meditation involves placing the right hand at various points of the upper body and head, presumably in line with chakras.
I would imagine that this could function as a version of vipassana, keeping the mind busy examining sensations.
Also of interest was the significant theta coherence emanating from AF3.