Attempt to connect failed, passed value not a func?

function hover_musicplayerframe()
	
end

---Definitions:
Music_Player_Frame = game.Players.LocalPlayer.PlayerGui.Music_Player.Music_Plyr
---
Music_Player_Frame.MouseEnter:connect(hover_musicplayerframe)
Music_Player_Frame.MouseLeave:connect(unhover_musicplayerframe)

It's a FrameGui that I am trying to connect to, why is it failing?

We need the full output.

I'll assume the error is on line 9.

Based on that, you have no function called unhover_musicplayerframe

It will be nil, thus not a function, and can not be connected to.

Define that function, problem solved.