Why is she too big to crate? My friend crates her Great Dane, dogs only need enough room to stand up and turn around in a crate, secondly, how long do you leave her? anything over 4 hours is too much, especially if she is your only dog. What times do you feed her? you could may be try changing her feed times, take her for a long walk before leaving her, don't leave her with food of any kind as even if she nibbles a bit of food it could stimulate her to empty herself. You can buy these plug-in things that give off pheromones or something to calm dogs with separation anxiety, so that could be worth a try. I have 4 big dogs and I always make certain they have 'been' before I go out anywhere, they have been trained to 'go' on command. Do you do plenty of general training with her each day? it gives a dog something else to focus on and believe me it wears them out mentally and physically, so they are more settled when left on their own, I always leave the radio on when I go out, and always on the station that they hear when I am at home, the idea of a tape recording of your voice worries me a bit, as I think if she hears your voice and can't find you then it may make her more anxious.