Dear Craig,
I'm afraid I don't know anything of your Graddad. But the 'Evening Follies' photo is fantastic!
The girl in the 2nd row, 2nd from right, is my Great-Grandmother. At that time her name was Jenny Spowart (she married George Grant in 1939).
I knew her very well, she used to talk about dancing. Her and Betty Walker (2nd row, 3rd from left) were 'Trix & Topse the tip top tappers'. She would have been about 15 or 16 in this photo, she used to do wee tap dancing steps when she was in her 80s. She passed in 2008 at the age of 87.
I wish I could've showed her the photo - she probably would have remembered everyone in it.
Betty Died very young - about ten years after this photo. My Granny (Jenny's daughter) remembers going to see her at her house in the Grassmarket when she was unwell).
As you can see from the photos I have posted, the man playing the piano is top left in your photo.
Hope you find this interesting
All the best,
Joe