thanx..................

I travel in a duo
with a similar friend,
several times you see me in your journey
I'm even round an unsuspected bend.

Total times I see you on your trip
comes to the number three,
I have a old shared history
With someone in your party.

But when you see me for the last time
I'll go out with a bang,
And even when I'm sorry
I'll sing for you in an unusual gang.

Who am I?