noun
A festival or event centered around musical performances.
毎年夏に大きな音楽祭が開かれる。
A big music festival is held every summer.
音楽会 is a general music concert or recital, while 音楽祭 specifically refers to a festival, often larger in scale and possibly spanning multiple days.
Compound of 音楽 (music) and 祭 (festival).