How does Sprechstimme differ from ordinary singing in Pierrot Lunaire?

In the context of musical performance, Sprechstimme—a term meaning "speech-voice"—differs from ordinary singing by functioning as a hybrid between speaking and singing.1

While ordinary singing is defined by the production of sustained musical tones through the coordinated use of the lungs, larynx, and vocal cavities to achieve specific pitch and timbre, Sprechstimme utilizes a technique where the tone quality of speech is heightened. In this style, the performer follows melodic contours indicated in the musical notation, but the voice does not maintain the sustained, pure tonal quality characteristic of traditional singing.21

Famously employed by Arnold Schoenberg in his 1912 work Pierrot Lunaire, Sprechstimme allows for a wider flexibility of vocal expression that moves beyond the conventional resources of a trained singer, effectively treating speech as a musically pitched element.12