A digital clarinet played by a human and timed by a metronome was used to record two playing control parameters, the breath control and the reed displacement, for 20 repeated performances. The regular behaviour of the parameters was extracted by averaging and the fluctuation was quantified by the standard deviation. It was concluded that the movement of the parameters seem to follow rules. When removing the fluctuations of the parameters by averaging over the repetitions, the result sounded less expressive, although it still seemed to be played by a human. The variation in timbre during the play, in particular within a note's duration, was observed and then fixed while the natural temporal envelope was kept. The result seemed unnatural, indicating that the variation of timbre is important for the naturalness.