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Joint speech occurs when two or more people utter the same thing at the same time. The definition includes choral recitation and chanting, and can extend across the boundary between ordinary speech and song. Shared timing and shared utterance content distinguish it from people merely talking simultaneously about different things.^[ref]

The topic has a tractable scientific core: how do separate speakers coordinate the timing of one utterance? A laboratory synchronous speech task can give two speakers the same text and record their voices separately. Corresponding acoustic landmarks then provide measurements rather than relying only on a listener's impression that the group sounds unified.^[ref]

Two properties need separate measurements. Speakers may produce identical words with a persistent time offset, or align their onsets while producing different words. Neither observation alone establishes both components of joint speech. A useful protocol therefore specifies the text, the events used to assess timing and the accepted deviation.

This turns a social activity into questions about speech perception, production and mutual adjustment. Findings from a controlled reading task identify what happened under those conditions; transferring them to a large spontaneous chant additionally requires evidence about that setting.