This work for piano strings organizes resonance phenomena in piano strings as musical material and applies them as a compositional principle. By depressing keys without sounding them, the piano strings are released, and the natural harmonics generated by striking adjacent intervals that resonate with the pre-depressed keys are meticulously structured and notated. By precisely controlling the combination of key depressions and struck notes, the sounds of the generated natural harmonics are selectively extracted. The struck notes merely function as a medium connecting the released piano strings and the natural harmonics. The musical structure is an acoustic phenomenon that emerges and fades within the piano's internal space, and is nothing other than a texture constructed by natural harmonics.