Donna Vivino - "Miss Byrd" (by Maltby & Shire) 

Sophie K Hi Sophie - I was at this concert. Maltby and Shire were personally involved and present. They loved it. And, who wants every person to perform everything the same way as someone else? This is clearly one of the best versions of this number ever performed. And, she’s doing almost exactly what’s in the piano conductor score. Perhaps you’ve never noticed that several sections are marked “Ad Lib”? Are you basing your criticism off of an original cast recording and expecting every performer to copy it?

Some of the differences sound less like choices and more like mistakes. That being said, I wish I could make mistakes/choices and sound like that!