Encyclopedia Britannica: Sprechstimme, (German: “speech-voice”), in music, a cross between speaking and singing in which the tone quality of speech is heightened and lowered in pitch along melodic contours indicated in the musical notation. Sprechstimme is frequently used in 20th-century music.!
Wikipedia: Sprechgesang (German: [ˈʃpʀɛçɡəˌzaŋ], “spoken singing”) and Sprechstimme (German: [ˈʃpʀɛçˌʃtɪmə], “spoken voice”) are expressionist vocal techniques between singing and speaking. Though sometimes used interchangeably, Sprechgesang is directly related to the operatic recitative manner of singing (in which pitches are sung, but the articulation is rapid and loose like speech), whereas Sprechstimme is closer to speech itself (because it does not emphasize any particular pitches).!