I looked through the rules but couldn't find anything.
So usually I would just go with what feels right. But there seem to be reasonable arguments for both answers in this case.
No - you cannot sing and conduct other verbal activities at the same time.
Yes - Bardic performaces don't have a set lyrics or tunes. Each bard will do them differently. The words and gestures of the spell can be woven into the performance.
In light of this, and the philosophy of "Say yes or roll the dice", my inclination is to go with "roll the dice" and allow it with a successful Perform check vs DC20 + Spell level.
However, before I made any decision, I thought I would ask here to see if I was missing anything. In particular I was concerned about unforeseen consequences.
Cheers
thotd
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