This works for me:
sFileSaveName = Application.GetSaveAsFilename(InitialFileName:="C:\blahblah\500 worst Songs\qwerty", fileFilter:="Excel Files (*.xlsx), *.xlsx")
as did this:
sFileSaveName = Application.GetSaveAsFilename(InitialFileName:="C:\blahblah\500 worst Songs\qwerty.xlsx", fileFilter:="Excel Files (*.xlsx), *.xlsx")