"the tune department" and "on top of his game"

[pink dragon]

Hello, could anybody help please?

Q1: Several writers and reviewers have dismissed this song as being below average in the tune department， to which I would say， what are you listening to?
What does "department" mean in this case?

Q2: The way the final bars build and then resolve is a songwriter absolutely on top of his game.
What does "game" mean in this case?

[Tdol]

1- We use 'department' colloquially to restrict or define an area, so ere it only means that the tune is dull- the video, lyrics, etc, could be fine
2- Performing well, doing a good job

[pink dragon]

Thank you tdol,
you are always a great help in my English department!

[Tdol]

You've got it.