No matter what keyboard or desktop environment or window manager I use, I always set the same multimedia keyboard shortcuts. This is to easily and quickly control the volume, move to the previous or next track, play/pause and toggle the microphone. I've settled on a scheme that is easily reachable and available on every keyboard and in my experience, on the numerous desktop environments and window managers that I've tried on Linux and the BSDs, doesn't conflict with any of the default keybindings, YMMV.
The scheme uses a Ctrl + Alt prefix along with a single character. These single characters are all on the right side of a split keyboard, for ease.
This layout gives me an easy, quick and universal multimedia control interface. Depending on what you're used to you may not like the use of two hands to operate these shortcuts, but for me using any kind of keyboard (including a split keyboard) your hands don't have to travel too far from the home row. As well as being within easy reach, the mnemonics are obvious and universal.