This paper examines French composer Gérard Grisey's representative work Modulations, focusing on the polyphonic texture in its second and fourth sections. Grisey innovatively constructs polyphonic textures based on the sound spectrum.In the second section, Grisey,by precisely controlling phase-shifting parameters, achieves a temporal dialogue of a single harmonic with itself within the spectrum. In the fourth section of Modulations, he builds the polyphonic texture through the instrumental synthesis of spectrum, creating interactions among four distinct timbres. The study reveals that the polyphonic texture in Modulations fundamentally embodies the aesthetic principles of spectral music, distinguishing itself from traditional polyphonic music in terms of aesthetics, generative logic, source material, and structural function.