Some questions on the use of つつある

Question

Harry has just evaded pursuit:

フィルチやスネープの足音も聞こえなくなり、ハリーは落ち着きを取り戻しつつあった。
The sound of Filch and Snape's footsteps faded away and Harry was recovering his composure.

"Harry was recovering his composure" is a pretty clumsy but, I think, literal translation. I'm wondering just how natural 落ち着きを取り戻しつつあった is? That's not the main point of the question though.

This is my first encounter with V+つつある. I get the impression that it is a formal construct and wouldn't normally be used in speech. Is this correct?

I'm also given to understand that is is useful to replace V+ている to disambiguate between a progressive action and a change of state. Is this the only reason to use it?

Finally, I believe that V+ているところだ would also unambiguously imply progressive action. How would that differ from V+つつある?

Answer 1

Unlike some of the other sentences you have asked about from this work, it sounds totally natural. And it's not that formal. You can use it in speech.

Although this might not have been the case originally, at least in current usage, [V ます-stem]-つつある seems to imply something is (slowly) starting to happen. It's close to [V ます-stem]-始めている. At least, that's how I understand it.

[V て-form]-いるところだ emphasizes that something is happening "right now" or at some reference point of time when that point is brought into focus by some other event.

フィルチやスネープの足音も聞こえなくなり、ハリーは落ち着きを取り戻しているところだった。

When I read this, I would expect the following part to explain what happened at that time as I would from the following incomplete sentence.

The sound of Filch and Snape's footsteps faded away and Harry was recovering his composure when ...