Greater Skald's Vigor prereq question ....

[Zabraxis]

I've been considering a Skald for my next PFS character and hit a snag w/ Greater Skald's Vigor while planning.

PFSRD wrote:

Prerequisite(s): Skald's Vigor, Perform (song) 10 ranks.

There's 9 Performance categories but no Performance(Song) and Skald specifies only oratory, percussion, sing, string, wind.

Is this just a typo for Perform(Sing)? If this was a home game, I'd just roll w/ that but it's for PFS and RAW applies. So RAW, I can't find a way to get Perform(Song.) Is there errata/faq that I missed?

[Saethori]

I think everybody just assumes it's supposed to be sing. I can't find any clarification on it.

Unlike most issues I might mention regarding PFS, this one I do not expect to see table variation. The idea that it's supposed to be sing instead of a skill that you literally cannot take seems more logical than the reverse.