It’s a bit misleading to identify Sprechstimme with a cabaret tradition. Schoenberg did indeed have a connection to Cabaret (he arranged for a Cabaret and also composed a number of songs, revived by Marni Nixon in the Monday Evening Concerts in the 1970’s), and while Viennese Cabaret singing was more speech-like than art song, the more immediate predecessor is the Sprechstimme as practiced in the Melodrama, an art music genre with origins in the late 19th century, in which the rhythm but not pitches of the spoken voice were typically notated. Schoenberg himself identified Pierrot as a Melodrama. Humperdinck was probably the leading composer of the Melodrama and there are notable Melodrama passages in several works by Weill.