the video looks choppy, but was smooth as usual
See how it’s done…
Afloat is a freeware application that adds really cool window features to most Mac applications (not iTunes). These features include adjusting a windows opacity, keeping windows afloat (or “always-on-top”), and making windows unclickable – so that you can use applications behind them.
Another cool little trick is holding Ctrl+Apple and two-finger-scrolling up or down to change the current window’s transparency. Very cool if you want to quickly look at the window below the current window – good for manually typing/copying info from one window to another without constantly flipping back-and-forth between the two.

This is the “Adjust Effects” menu: