Unsure if anyone else has done this, but adding the following paths to /mnt/sdcard/will add your own ringtones, alarms, and notifications to available sounds:
 You can do this in /mnt/sdcard/ext_sd/ as well.
Adding custom sound sets in 'Personalize' (part of HTC Sense 3.0 I presume), I can assign these custom sounds to events, e.g. ring, default notification, e-mail, message, calendar. But when I mount the phone using HTC Sync mode as "Disc Drive," the mappings are changed to default sounds (T-Jingle for a T-mobile phone), and the sets lose their sound assignments. They seem to recover when I then change HTC Sync to "Charge only."
Another member of other forums complained that this would happen to him after a restart. I confirmed his issue and found a workaround, of sorts.
1. Hold power button, select Restart.
2. Wait for phone to restart completely.
3. Unlock (if screen lock enabled).
4. Click Personalize.
5. Click any Sound set.
=> They are all showing their sounds correctly, but not playable. In the Personalize screen, all notification sounds are displayed as "T-Jingle" (the one in ROM, I presume).
3. Unlock phone.
4. Connect to a PC.
5. Select USB Sync mode "Mount as a disk drive."
6. Wait 10 secs.
7. Click USB sync in Notifications.
8. Change connection to "Charge only."
=> "Preparing phone storage," "Preparing SD card," ....
9. Click Personalize.
10. Click Sound sets.
=> All Sound sets' custom sound assignments are correct, AND functional.
Seems that on reboot, HTC Sense is not waiting for full mount of /sd_card before assigning event sounds, and defaults to "T-Jingle." I've read anecdotes that system programs that are moved to /mnt/sdcard/ storage will fail to start as /sdcard/ isn't mounted yet as init.d type startup scripts are run.
Definitely some bugs here (with multiple options for resolution). Again, posted on HTC support forums but those are now failing on login or reply attempt.
Another workaround ... put the /media/ folder on /sdcard2 aka /mnt/sdcard/ext_sd/ ... somehow, Personalization remounts that after a reboot and the mappings are valid.
I was having this on my HTC Sensation, with the downloaded HTC sound sets that are stored in sdcard/ringtones etc.
I did a few factory resets, and of course I cant say for sure, but it seems to be after Google+ is installed, is when the sound problems starts on my phone. Google+ installs a special notification sound file I think the system gets stuck on when scanning the sdcard for audio files, and maybe this delay is whats causing the problem.
Ive been installing other apps and stuff, restarting etc. and have not had my ringtones corrupted like before, since not installing Google+. So it would be interesting to see if other HTC gingerbread users, who have this problem or similar have Google+ installed. Im probably wrong, but thanks to your article, if it does come back, I'll just move my sounds to the internal memory.
Don't know about Google+, but something installed /mnt/sdcard/media/audio/notifications/facebook_ringtone_pop.m4a . It doesn't seem to impede finding notifications on /mnt/sdcard/ext_sd/media/...
Retrieving data ...