Videos of him rapping a cappella while standing on a conference table have been posted on YouTube. On his website afterward, West posted a letter to Facebook, thanking the staff for their support:
"Your energy was a gift so electric, so genuine, that it really helped me give my best."
An e-mail request for comment from Facebook was not immediately returned.
West's new as-of-yet untitled album is expected to be released Sept. 14.