I have a USB key over OTG with my Nexus. Using Stickmount or the latest ES File Explorer; the key mounts, I see it at /data/media/0/usbStorage/sda1/, /sdcard/usbStorage/sda1 and /storage/sda1, I can read and write files, it doesn't show up under Settings > Storage, and I can't select it in Google Play Music. I'm assuming something like the Meenova would show the exact same issue.
Anyone know why this is a Nexus issue? Anyone know where the sdcard is mounted on working devices? Has anyone used a ROM that works with Google Music and OTG?