I lol'd at that. I only mean it as an empowerment. I believe in all of your abilities to craft the most awesome games for your groups, sincerely.Horrible idea, OP, don't do this. "That is awesome" is the part you should concentrate on, skip the rest. "Screw the rules" is about as helpful as a fist to the face when somebody is asking a rules question...
I do however, disagree that "that is awesome" be the guidepost here. It is a matter of style, not right or wrong.
Personally, I don't think it "nerfs" the class to apply a little sense to the situation. How do you sing a song and verbally cast at the same time? That's not awesome, that's rules-encoded dumbness. Hence the comment about the axe. GMs should feel free to hack away at dumb rules. It's how we ended up with things like PF in the first place.
The 2E Bard couldn't do anything but move while engaging this same function. It *is* awesome to have them fighting while singing, but geez, a -1 is seen as ruining the class? How about a -3 that becomes a +3 at high levels?
There are many possibilities here. Make what you will of it. I confess to being somewhat of a ninja, in that I have only played a handful of PF sessions, and have only GMd Mentzer--->3.x, and mean no disrespect to the PF rules, other than to say screw 'em and have fun. Peace owt -