What should I do when the Scale Warriors boss uses his shield?

In RockSmith 2014, there's a game called Scale Warriors. At the end of each level, you go up against a big red dude. Sometimes when I try to hit Big Red, he raises a shield to block the attack. Unlike the shield in Ducks Redux, this one does not seem to be affected by taking a series of hits. And because no other scale notes are lit up, it doesn't seem possible to retreat, either.

Are my Scale Warriors inevitably going to take damage once Big Red raises his shield? Or is there something I can do to avoid it?

Solution 1:

It turns out that my thinking was exactly the opposite of what the game designers intended: When the boss raises his shield, you will only take damage if you strike it again. So, the correct move is to mute the string.