Question about a Key..

I got a Binding Of Isaac key, but i already own the game through a tradable copy, but i was missing the "The Binding of Isaac soundtrack" DLC, and i didn't know that...so i decided to try the key in my steam account just to check if it's valid, expecting something like "Product already owned", but oh no, it was activated in my account because i was missing that Soundtrack DLC, yeah, i felt retarded, but i was wondering if that key stills have the game? i mean..can it be used in another account and the game will be activated without the Soundtrack DLC?

That's pretty much it..thanks in advance.