Occasional music refers to a form of music in which musicians introduce accidental factors into the creative process or performance process in their creation. Specific methods include: using random techniques when composing works, allowing performers to improvise without any prompts, or even to modify the instrument Or add off-track sounds to play tracks. According to the definition above, Which of the following options are not accidental music:. ['The conductor randomly decides the number of instruments used, the length of the performance and the number of participants before the performance.', 'Insert rubber and iron nails into the piano strings to simulate the sound of percussion to play music.', 'Use the dice and toss coins to determine the pitch, velocity, and orchestration of the work and create a score.', 'The player remains silent, at this time, occasional applause and laughter constitute the music.']