Although it had already been employed as early as 1617 by Biagio Marini and again in 1621 by Giovanni Battista Riccio, the bowed tremolo was invented in 1624 by the early 17th-century composer Claudio Monteverdi, and, written as repeated semiquavers (sixteenth notes), used for the "stile concitato" effects in "Il combattimento di Tancredi e Clorinda". The "measured tremolo", presumably played with rhythmic regularity, was invented to add dramatic intensity to string accompaniment and contrast with regular tenuto strokes. However, it was not till the time of Gluck that the real tremolo became an accepted method of tone production. Four other types of historical tremolos include the obsolete "undulating tremolo", the "bowed tremolo", the "fingered tremolo" (or slurred tremolo), and the "bowed-and-fingered tremolo".