$ xmodmap -e 'keysym Alt_R = Multi_key'     # Set it right Alt
$ xmodmap -e 'keysym Caps_Lock = Multi_key' # Set it to Caps Lock
$ xmodmap -e 'keysym F12 = Multi_key'       # You're free to use *any* key, like F12

! Set compose key
keysym Alt_R = Multi_key

setxkbmap -option compose:ralt  # Right alt
setxkbmap -option compose:caps  # Caps Lock

Section "InputDevice"
    Identifier "Keyboard0"
    Driver "kbd"
    Option "XkbOptions" "compose:ralt"
    #Option "XkbOptions" "compose:caps"
EndSection

Section "InputClass"
    Identifier "Set compose key"
    MatchIsKeyboard "on"
    Option "XkbOptions" "compose:ralt"
EndSection

keycode 133 = dead_greek NoSymbol SuperR

http://zuttobenkyou.wordpress.com/2011/08/24/xorg-using-the-us-international-altgr-intl-variant-keyboard-layout/
http://stackoverflow.com/questions/14922007/how-to-enter-greek-alpha-under-xor
keycode 48 = dead_grave apostrophe


<dead_grave> <space>       : "`"   grave # GRAVE ACCENT
<dead_grave> <dead_grave>  : "`"   grave # GRAVE ACCENT
<dead_grave> <a>           : "À"   agrave # LATIN CAPITAL LETTER A WITH GRAVE

include "%L"

<Multi_key> <quotedbl> <a> : "ä" adiaeresis

<Multi_key> <a>          :  "ä" adiaeresis
<Multi_key> <b> <b>      :  "ä" adiaeresis
<Multi_key> <c> <c> <c>  :  "ä" adiaeresis
<Multi_key> Alt <d>      :  "ä" adiaeresis
<Multi_key> Ctrl <e>     :  "ä" adiaeresis

# Make compose key work for GTK, Qt
export GTK_IM_MODULE=xim
export QT_IM_MODULE=xim

# Make compose key work for GTK, Qt
setenv GTK_IM_MODULE xim
setenv QT_IM_MODULE xim

<Multi_key> <i> <b> : "NL65AEGO0721647952"

Position of Compose key
    +------------------------------------------------------+
    |Option                Description                     |
    +------------------------------------------------------+
    |compose:ralt          Right Alt                       |
    |compose:lwin          Left Win                        |
    |compose:lwin-altgr    3rd level of Left Win           |
    |compose:rwin          Right Win                       |
    |compose:rwin-altgr    3rd level of Right Win          |
    |compose:menu          Menu                            |
    |compose:menu-altgr    3rd level of Menu               |
    |compose:lctrl         Left Ctrl                       |
    |compose:lctrl-altgr   3rd level of Left Ctrl          |
    |compose:rctrl         Right Ctrl                      |
    |compose:rctrl-altgr   3rd level of Right Ctrl         |
    |compose:caps          Caps Lock                       |
    |compose:caps-altgr    3rd level of Caps Lock          |
    |compose:102           <Less/Greater>                  |
    |compose:102-altgr     3rd level of <Less/Greater>     |
    |compose:paus          Pause                           |
    |compose:prsc          PrtSc                           |
    |compose:sclk          Scroll Lock                     |
    +------------------------------------------------------+