intro:
e-------------0-2--------------------0-2-------------------2--0-------3-------
B-------3--------------3-------3-----------------------3-----------3----3---3-
G----2-----2--------2-------2-----2------------0-------0-------------0----0---
D-0-----------------------4-----------------0----------2----------------------
A--------------------------------------------------3--------------------------
E-----------------------------------------------------------------------------
zwr.D C G (x3)
D G
ref.A B C G