Adding sound to LXDE start

Simple.

Make a .desktop file and put it in ~/.config/autostart (if this dir doesn't exist, then create it):
# mkdir ~/.config/autostart
#touch ~/.config/autostart/sound.desktop

As you see, my file's named sound.desktop

Which contents may be:

[Desktop Entry]
Name=Sound
Terminal=true
Type=Application
Exec=mplayer /home/pibarnas/Downloads/221359__melliug__newmessage.mp3

I've downloaded mine from freesound.org. There's a lot of sounds there. Enjoy!