The term 'Speak in a Singing Voice' can be summarized by the crossword solution 'INTONE, ' which is a six-letter word. Intoning is the act of speaking or singing with a steady, continuous tone, usually in a low pitch. It is often used to emphasize certain words or phrases and can be used to create a more melodic sound. Intoning is commonly used in religious ceremonies, poetry readings, and musical performances.