I think they mention that, akin to Perform (stabbing), you cannot use Perform (weapon drill) for Bardic Music effects.

Perform (oratory) covers chanting and such, and as the DM, I think I'm going to say that you can maintain a bardic music effect while raging as long as you're using some kind of rhythmic song or chant (So, Perform (sing) or (oratory)). I don't think playing the lute, for example, is going to work during a rage.

The standard action to initiate a song requires too much concentration on the part of a raging barbarian, but as a free action, the maintaining is easy.

This seems to make the most sense for my game.