Can the alert sound in Mountain Lion's notification center be customized? Is there a way to change the default "Basso" alert sound in Mountain Lion's Notification Center?  What I'd really like is support for application-specific notification sounds, so I can tell without looking at the screen whether a notification is from, say Mail vs. iCal.  Is this possible, and if so, is it something the application controls or NC controls?  If not, at least the ability to change the sound from Basso to something else would be an improvement.
An even better Idea is to got to ~/Library/Sounds and create a sound file with the same name as Basso.aiff and it will supersede Basso without the need for deleting a system sound file.