Dialogs should not be on top of all apps

Which OS are you using?

Also true (dialogs stay on top when they shouldn't) on Ubuntu 14.10 (3e673e6), so I assume it is probably true on all platforms.

Other points to note:
- This is not the behaviour of other programs (e.g. GIMP, even when "Single Window Mode" is deactivated).
- True for the "Mixer", "Play Panel" and "Start Centre" etc. These all stay on top when they shouldn't.
- Not true for floating toolbars (e.g. "Pallets", "Inspector"). These go behind other windows as they should.
- Also not true for for windows like "Edit -> Preferences..." or "Styles -> General...".

See these perhaps:

#15629: Mac: Play Panel doesn't float above main window
#37831: Keep master palette at the top in the window stack

Fixed in 1d4556b526

To fix this, in file "mscore/mixer.cpp" simply remove the line:

   setWindowFlags(this->windowFlags() | Qt::WindowStaysOnTopHint);

This does the trick because the stay-on-top attribute was already implied by making the main window a "parent" and the Mixer a "child" of the main window. However, someone with a Max will need to see if this breaks the fix to #15629: Mac: Play Panel doesn't float above main window. If it works it should be safe to make the same change in "playpanel.cpp", "masterpalette.cpp" and "synthcontrol.cpp" too.

Also, while you're at it you might consider replacing the line:

   setWindowFlags(Qt::Dialog);

with:

   setWindowFlags(Qt::Tool);

This gets rid of the silly "Maximize" button which doesn't really make sense in the Mixer, Play Panel or Synthesizer. (See: //qt-project.org/doc/qt-4.8/qt.html#WindowType-enum .)
)
I suppose it might make sense to have a "Maximize" option for the Master Palette in a multi-monitor setup.

It appears somebody beat me to it and fixed it, but my previous comment is still relevant for removing the "Maximise" button.

I changed some top level windows to "Tool" as suggested. On my kubuntu it removes the minimize button, the maximize button is still there...

Strange! It works perfectly on my Ubuntu 14.10. Also, I never had a "Minimize" option, even with Qt::Dialog:

My Windows 8.1u1 also only shows the "X" on these floating windows. Only the Master Palette shows an extra icon on the left.

Automatically closed -- issue fixed for 2 weeks with no activity.

I just updated MuseScore 2 for Windows 7 to get rid of the bug, but it appears the bug is not fixed yet for this OS.

2.0 Beta 2 I assume? If so: it had been fixed later, 2.0 RC should be out any minute now, so wait a bit or use the latest available nightly build.