AHA! I figured out how to get all your music from USB storage to show up on any music player!
First, you need root access.
Once you're rooted, download this app:
https://play.google.com/store/apps/d...e.fmount&hl=en
What foldermount does is essentially creates a link to your external USB mounts (that are not scanned by the system "media storage" app, that most music players use to detect music) and puts those links inside your internal sdcard folder so that media storage can scan those files!
So basically you just have to set the source path like this /mnt/sdcard/Music/ (or wherever you want the USB to show up)
and your destination as /mnt/usb/[drive name mine is sdb1]/Music/
Set it to launch at boot and then reboot and you'll see it activate in the notification bar upon reboot, then your music will show up in all your music players!
Note: This doesn't just work for music, it can actually be used to remap your micro SD card as internal storage for more app and data space if you really get into it. This could really change the game for this HU, you could use it to store Sygic map packs on your micro SD, change download paths to USB or Micro SD, or put whole apps on the micro SD card if you're so inclined (your results may vary), enjoy!
Edit: I originally posted the directions backwards, source should be internal and destination should be usb drive.