So I was reading the UI guidelines here on maemo.org and it says you shouldnt use a GTK toolbar unless only one content item is visible (such as an edit screen).

If an app has multiple windows, as most do, where are we supposed to put our window icons/buttons?

For example - let's take the ipod music app on the iphone/touch. Along the bottom it has 5 icons, Playlists, Artists, Songs, Albums and [... More], with each bringing up a slightly different interface for different things - but the toolbar stays.

If you were to require a similar window changing functionality, what are the UI guidelines that apply?

How does one allow the user to always be able to select from a set of windows (a maemo example would be when you wish to provide the user with a view windows, categories, tags, search, settings, etc).