Default volume keybindings do not work when audio is switched to HDMI

The default keybindings for changing the volume in Lubuntu are found in /usr/share/lubuntu/openbox/rc.xml:

    <!-- Keybinding for Volume management -->
    <keybind key="XF86AudioRaiseVolume">
        <action name="Execute">
            <command>amixer -q sset Master 3%+ unmute</command>
        </action>
    </keybind>
    <keybind key="XF86AudioLowerVolume">
        <action name="Execute">
            <command>amixer -q sset Master 3%- unmute</command>
        </action>
    </keybind>
    <keybind key="XF86AudioMute">
        <action name="Execute">
            <command>amixer -q sset Master toggle</command>
        </action>
    </keybind>

If you are running Lubuntu on a laptop (which has the built-in audio card with analog audio), those commands work correctly.

However, when you switch the audio to HDMI, those commands do not work anymore.

To switch to HDMI audio:
    pacmd set-card-profile 0 output:hdmi-stereo+input:analog-stereo

To switch back to analog audio:
    pacmd set-card-profile 0 output:analog-stereo+input:analog-stereo

Alternatively, right-click on the speaker icon at lxpanel, select "Volume Control Settings", and change the active profile at the "Configuration" tab.

The solution for this bug is quite simple: just add "-D pulse" to each of those commands, like this:

    <!-- Keybinding for Volume management -->
    <keybind key="XF86AudioRaiseVolume">
      <action name="Execute">
        <command>amixer -q -D pulse sset Master 3%+ unmute</command>
      </action>
    </keybind>
    <keybind key="XF86AudioLowerVolume">
      <action name="Execute">
        <command>amixer -q -D pulse sset Master 3%- unmute</command>
      </action>
    </keybind>
    <keybind key="XF86AudioMute">
      <action name="Execute">
        <command>amixer -q -D pulse sset Master toggle</command>
      </action>
    </keybind>

This solution was found here:
http://ubuntuforums.org/showthread.php?t=1956323
https://askubuntu.com/questions/349541/finding-volume-raise-lower-commands/

This solution, however, will not update the user's own configuration file, and probably it shouldn't try anyway.