The strings which correspond to the circled pitches are to be prepared with dimes. These notes on the piano have three strings per note, so the dime may be wedged between the three strings. The pitches created will be lower than the written pitch. The target created pitches for d, e# and f% are a, c# and d respectively. The dimes may be adjusted along the length of the string to achieve these target pitches. The strings which correspond to these circled pitches (which are an octave above where written) should be prepared with the rubber insulation of a wire. The insulation should be stripped from the wire and then a cut must be length-wise along one side of the remaining insulating tube. These tubes will be wrapped around each of the three strings which create these pitches. The target pitches for c, e, and fare a, c# and d respectively. The pitches may be adjusted by altering the length of the insulation added to the strings, but these pitches may be slightly out of tune to create a more abstract prepared sound.
Schaar, Jesse, "Acoustic Exploration for Prepared Piano" (2007). Compositions. Paper 10.