Hi. I realize this thread is from a few weeks ago, so I don't know if you've figured it out already, but there's a few things that come to mind. First is, under "volumes" uncheck the link system and ringtone volumes". Then, under "system" look at the default notification sound... there you should be able to change the sound. I use liquid 2.10, and for me it works flawlessly. I've read a lot here about people having problems running 4.3 roms but I've been lucky I guess. Well, first time I ran into a problem as I used titanium to restore apps and data (caught in boot loop) and I was told that there's the problem with apps from 4.2 to 4.3. So after restoring my nandroid I used helium to selectively backup and restore app data, not a problem since. Also, the flash method is unusual to me. Supposed to wipe, rewipe everything, then flash the Rom, boot up, set up phone (everything but Google apps), then power off, boot back into recovery and flash gapps separately. I haven't run into anything not working. I have a different ringtone for calls and a separate sound for notifications. You probably know all this stuff already, but I'm only trying to describe what I did and how it works for me.
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