How can I play different sounds each time I startup?

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http://askubuntu.com – I have read questions on Changing startup sound in Ubuntu and Changing startup music in Ubuntu. I understand how to rename 'desktop-login.ogg' and copy the sound I want as 'desktop-login.ogg'. My question is - is there a way I can play different sounds each time I login? It may sound silly, but if possible I would like to play different sounds. I am guessing that this may be perhaps possible by running some kind of script which replaces/renames the desktop-login.ogg file each time I shutdown, so that a new file is ready to be played on the next startup. But I don't know how to copy a new (HowTos)