This treatise studies and compares two twentieth-century works and the pianistic challenges they exhibit: Karlheinz Stockhausen’s Klavierstück VII and Tristan Murail’s La Mandragore. Historical background is provided on Karlheinz Stockhausen and Tristan Murail as compositional pupils of Olivier Messiaen. Messiaen’s consideration of sound components such as timbre and resonance are discussed, including Stockhausen’s continuation of this trajectory. The French spectral school is explored; it evolved in the 1970s with some of Messiaen’s pupils, most notably Murail. Timbre and timbral-harmonic complexes are the focus of spectral works rather than melody, harmony, or tone row processes. In addition to timbre being used as a formal component in spectral compositions, auditory perception of timbre is the main compositional goal in these works. Timbre is explored in piano music through long-lasting pedals and consideration of the overtone series. A performance guide for Stockhausen’s Klavierstück VII and Murail’s La Mandragore is provided to facilitate the learning process of these two works. These two piano pieces are both undervalued and underperformed, and this treatise seeks to inspire other musicians to listen to, and hopefully to perform, these great works.