At night when there is complete silence, do puraka, clsoe the ears, hold breath comfortably (kumbhaka) and hear the word or music (naad), which echoes within. Concentrate mind on that music, whatever words come up, try to concentrate in their rhythm whole-heartedly. The words of the music keep changing slowly. Sometimes music of a cricket, and sometimes that of a bumblebee, bell, drum, clouds etc is experienced. After a regular practice, the music can be heard by keeping the ears open also and the sadhaka’s mind remains in it by itself.