Just got one, you can add any mp3 sound according to the manual. Comes with 100 sounds divided into 17 folders. If you buy it from Rick Pailet at Verminators, he adds 25 additional sounds.
The SD card can be plugged into your computer and add or take away folders and sounds like normal computer files.
For what it's worth, I took it out the first time and called in a bobcat and a coyote on the only stand I've made with it so far. Coyote came in 200 yards downwind and caught my scent. Maybe next time.