Control master audio volume with Siri

This separation of "sound effects" and "games/music" exists in iPod Touch 4 as well. There is no way for tuning a master volume on these devices. But you can set the "sound effects" volume as constant (Settings - Sounds - turn off Change with buttons) and pressing volume buttons will only change the "games/music" volume.

I ran into issues where my audio controls were disabled similar to what you describe. I can't be sure it's the same issue, but in my case, killing the Core Audio process fixed it.

Open up Terminal and enter this command:

sudo kill -9 `ps ax | grep 'coreaudio[a-z]' | awk '{print $1}'`

You'll be prompted to enter your password, but that should find and kill the proper process, which will then auto-restart. Your volume control should come back to normal within a few seconds if this is indeed the problem.