"There is ... large piano in the hall?" What article goes in here?

Question

There is ... large piano in the hall?

I think there is should put "the" before "large piano" article because we use "the" before musical instruments. But in the grammar book wrote "a" article before "large piano". Why?

Answer 1

We use "the" before musical instruments when discussing them generally, in an abstract sense, for example "Jane can play the piano", "Kumar is learning to play the flute", but otherwise the same rules about articles apply. There is a large piano in the hall, I have a small trumpet in my suitcase, whose is the guitar on the table?