If a card has a bold word like Fellowship or Archery followed by an action, then you must fully perform one action before performing another (From the Comprehensive Rulebook: Each phase action must be completely performed before another phase action can be performed. Phase actions cannot be combined.)
So you can't combine the effects of Rumil and Orophin or the effects of the pipes. To give another example, you cannot combine
Pippin, Mr. Took with
The Prancing Pony*, because they are both separate phase actions.
Shadowplay works a bit differently, however, and I've never used the card, so hopefully someone else will clarify this. It's not a phase action, it simply says "Each time a minion is played", so you can exert multiple hobbits to exert one minion multiple times (Or exert several minions) but you need multiple copies of
Shadowplay to do this because each one says "limit once per turn". So while you could exert a minion 4 times, it would cost 4 exertions.
Hope that makes things a bit clearer
