I remember this problem when i had my dinc 4G I before s-off the device. I can't remember the EXACT steps to get it to show up, but i got it to show up as a shortcut. I don't have this phone YET, but i will tell you what i can remember.
1) Download ES file explorer.
2) Go into the device system/app folder and locate the HTCsound recorder apk , and try to install it. If you are not rooted it will fail. That is fine.
3) In ES file explorer go to tools - > app manager then system apps and find the htc sound recorder.
4) Long press it until it checks and then go to the menu and choose send to desktop.
This is how i got a SHORTCUT to the app on my non rooted dinc 4G.
I honestly do not know if it will work with this phone but though i throw it out to see if someone can try.