These are two piano compositions by Don Robertson from 1967. The first, on the left, is very quiet, the performer beginning with the first quadrant, then performing the other quadrants in any order and any number of times, always ending with the first quadrant. 
    The second piece on the right contains six sections that may be performed in any order. Each section is repeated continually until the performer decides to move to another section. The piece ends after all six sections have been performed at least one time.