Looked at the list and I have no clue.
The big hint was the birthday thing mentioned (someone's birthday 122 years ago today, and I looked up birthdays from 122 years ago)... and, in Wednesday's set's backsell, he mentioned "Hold Your Head Up" was a preview of this set's theme. So I'm pretty sure I know what the theme is, though I haven't listened yet, and I'm not sure the songs all meet the requirement. Though Ray Charles almost certainly does.
That's all the hints I'm giving.
ETA: Listening now, and DW gives it away just before the set. And it's right up front with the Ray Charles track. BOS Brother Ray.