I think we've got some music biz jargon here:
【我们恋爱吧 第二季】EP12 @ ～20:09
The person speaking often speaks of his band, so it is likely that 乐 is short for: 乐队. Of course, less specifically it could just be short for 音乐.
助 is a little more ambiguous. It could be 助唱, 助理 or something else.
It doesn't seem like a very common word. There aren't a lot of query hits for it online.