When using CMD-Tab, how to re-open the app's main window?

I hit this problem often when interacting with some Apple applications, mainly Messages and iTunes.

After starting a song with iTunes, to clear my screen and get back to work I close the iTunes window with CMD-W. The iTunes application is still running in my Dock and playing music.

After some time, I want to switch to a different album. I CMD-Tab to select the iTunes application. iTunes is focused in the menu bar. But no window is shown, because I previously closed the window.

This workflow occurs for all apps, and is not usually a problem. If I switch to Safari and no window is open, I simply press CMD-T or CMD-N to open a new tab or new window.

With iTunes, I press CMD-N and nothing happens. No iTunes window is created or shown. The Application is focused, but the main window is not re-opened if it is currently closed.

I end up clicking on the Dock, which (in addition to focusing the application) opens a new iTunes window if that window was previously closed.

This breaks my (usually more efficient) CMD-Tab workflow. If I'm forced to click the iTunes dock icon, I may as well just click the dock icon from the start and forgo the keyboard shortcut.

Messages has a similar problem. If I receive a desktop notification and use CMD-Tab to open Messages to respond, the application will be focused but no window will be opened. I can press CMD-N, which in Message's case does open a new window, but the "new message" cell will be opened rather than the existing conversation I had open and now want to respond to.

When clicking the Dock icon or opening the app via a Spotlight Search, if the main window is not open then it will be re-opened. Is there a way to force this behavior for CMD-Tab app selection?

How do I show the main window when the Application is focused via CMD-Tab?

Several applications including iTunes let you switch views by using CMD +<number>. CMD + 0 will give you the main window. But some applications like iTunes offer different views.

Just try CMD+tab to iTunes and then variate between CMD + 1 to 9 to see which view you like. In the screenshot below you can see the different options for iTunes. Messages only has the option CMD + 0.

There exists a shortcut for that, though it requires certain dexterity:

Command-Tab to the app, but then, before releasing Command, hold Option.

If you then release Command while still holding Option, the window should pop open.

It's just like clicking in the app icon in the Dock (if there are no windows open, one opens; if there is a minimized window, it appears again).