When Welcome to Rathe was released, we took the position that Ironsong Response could not be played if reprise was not active. We have since come to the realization that this is neither intuitive to players or supportive of design space we want to explore in the future.
Effective immediately, Ironsong Response can be played regardless of whether the reprise effect is active or not. Obviously, if reprise is not active, Ironsong Response does nothing. However, playing out a card that does nothing may well be the correct play, if there is greater value in clearing the arsenal or cards in hand.