Repetition in music or (echo) time delay

Repetition is everywhere.


While playing again the D minor prelude - Bach from the well tempered clavier it was wandered again how amazing it sounds at about middle of first page.


Bass going down


Fa Mi Re Do Si La


Then


Mib De Do Sib La Sol


And something amazing happening at the right hand...


Then while waiting for public transport the score had been looked at carefully.


In fact melody on right hand does


FA Mi Re Do Si La a few seconds latter


and then


Mi Re Do Si La Sol a few seconds latter again after walking down bass