Rdio requires the discrete graphics card on systems which support dynamic switching. This is annoying, since playing audio shouldn’t require intense graphics.
To get around this limitation, we can update the Rdio app’s Info.plist to inform the system that it supports the integrated card. We can accomplish this with the following command:
defaults write /Applications/Rdio.app/Contents/Info.plist NSSupportsAutomaticGraphicsSwitching -bool YES
To revert back to forcing the discrete card, we can remove the key:
defaults delete /Applications/Rdio.app/Contents/Info.plist NSSupportsAutomaticGraphicsSwitching
Incidentally, gfxCardStatus is an excellent tool for monitoring graphics card changes and manually switching between cards.