It also contains one of the most striking examples of PERSON@1 ' experimentalism : in the second movement , he instructs the pianist to use a piece of wood to produce a dense but generally very soft cluster chord .

It also has an interesting example of one of PERSON@1 ' experiments : in the second movement , he tells the pianist to use a NUMBER@1 NUMBER@2 in -LRB- NUMBER@3 cm -RRB- piece of wood to make a thick but soft cluster chord .
