This is a difficult 术语 to 定义 since it pertains to such a wide variety of 多样 樂/乐 practices but most simply put is the act of 樂/乐 决策 during 表演 From the 透视 of Western 樂/乐 传统 it will 经常 relate to 关系 between 决定 made by composers and 通常 written down through 樂/乐 记谱法 and those made by 表演者 as part of their 解释 of a 作曲 决策 may relate to 微观层 方面 of the 樂/乐 表面 or macro-level 方面 of 结构 and 形（曲）式 即兴 may rely upon some 度 of 预定 framework whether notationally or otherwise culturally mediated During the twentieth century significant 樂/乐 发展 for which 即兴 was integral were 爵士 and subsequently 自由 爵士 which loosened 用 of frameworks of 谐/泛音 progression melodic 发展 关系 between 表演者 and 樂/乐 temporality along with some 形式 of 实验 rock The 实验 樂/乐 动作 that emerged in the UK during the 1960s privileged 即兴 with 社会 and 政治 as well as 声音 动机 即兴 too was an influence upon the 发展 of American minimalist 樂/乐 The 术语 自由 即兴 is used to 描述 表演 that makes extremely 限制 用 of pre-made 决定 or frameworks and is in 原则 at least completely stylistically open-ended

As in other 形式 of 当代 樂/乐 即兴 in 電聲學/电声学 樂/乐 may be closely 相关 to 形式 of 偶然 or 不确定 So-called 现场 电子 is now long 确定（建立） and 多样 即兴 and 偶然 often meet where 音乐家 have built custom 电子 乐器 and 设备 for 例如 in the 'composing inside electronics' 美学 联合 with David Tudor and 表演 with 'feedback instruments' The 数字 connectivity offered through 算機/计算机 技术 has allowed 音乐家 to experiment with new 模式 of 集 and 协作 决策 on stage Also 即兴 can be 已有 in 活动 outside of conventional 性能 for 例如 in the 用 made by many composers of 模拟 工作室 设备 in 塑形 声波 材料 and the 决策 made by participants in 实时 活动 with 声波 across 分布 networks 即兴 is also an integral 方面 of DJ culture and 唱机主义