As tonality reached its climax during mid-to-late eighteenth century, however, several composers were experimenting writing with various harmonic procedures, which drew attention especially to the nineteenth century composers, from Chopin and the equilibrium between diatonicism and chromaticism to Wagner with the endless chromatic melody. The trend continued toward early twentieth century especially in the hands of Debussy and Schoenberg with their innovations that influenced many generations, although both represented two different musical and artistic directions: Debussy with the experiment with harmonic timbre and Schoenberg with the new “scale” construction respectively. The purpose of this research is to provide analytical evidence of radical harmonic timbre and exhausted tonal harmony resulting from the various use of artificial scales in Debussy’s music (especially since c.1889) through the analyses of Debussy’s two piano works. The two works include L’isle Joyeuse (1904) and Et la lune descend sur le temple qui fut (1910). The method includes historical analysis, descriptive and prescriptive analysis, leading to the conclusion that Debussy demonstrates new approaches to scale, harmony, tonality and overall color that became such significant contributions to the later twentieth-century music.