> Don’t they use the same rolling stock and cover very similar stations?

Same stock, yes.

But stations different. Circle is Zone 1 and so almost entierely covered except for very short sections. But District has a lot of open track sections.

The Bakerloo sounds are indeed pretty distinctive (I lived near Kilburn Park for a while and knew it well!). But I think the easiest of all is the Jubilee line. Those melodic sounds from the traction motors that rapidly change pitch when accelerating/decelerating are so distinctive and unique.

Jubilee I found pretty easy too