It's probably that awful music that wakes me up every morning.
问题描述：
It's probably that awful music that wakes me up every morning.
答
it 没有特定的指什么东西,或者可以说,it指的就是那个说不清的、不特定的东西
口语里这样很普遍
根据回答,语境估计是有人问
”You seem tired. Haven't you been sleeping well?"
"你似乎有些疲劳.最近没睡好吗?”
回答
It's probably that awful music that wakes me up every morning.
估计是那难听的音乐每天早晨把我给吵醒
（不算是特别通畅的翻译但基本是这么说的）
这里 It 指 “原因”, It is probably ... 原因估计是.
尽管提问这没有明确的问
“你为什么这么疲劳呢?”
可以想象他的问题就被这么理解了. 两方都有些含蓄,但是人际交往中难免的.