This article examines the role of whistling as an elusive voice in the literary world from around the third century onward. It argues that as an alternative to normalized forms of vocal, musical, and poetic expression, whistling destabilized, blurred, and reconfigured notions of voice, language, writing, and music within the larger context of Six Dynasties thought and aesthetics. Despite the wide range of vocalizations (e.g., wailing, the tiger's roar) associated with whistling in premodern China, the whistling examined in this article refers to a particular vocal art commonly practiced by the literati. It reached its height around the third century, signaled by a rise in literary texts that illustrate its musical features, elaborate its mechanism, and tell stories about whistlers. An analysis of two main texts on whistling, Rhapsody on Whistling (third century) and Principles of Whistling (circa eighth century), uncovers the act of whistling as a gap: it is not yet a voice, not quite a kind of music, and it is beyond the realm of language. The whistler does not produce the whistling; it is his breath—passing through a bodily gap—that activates his body as a musical instrument, making the whistled sound an echo even before it sounds.