I imagine that would be quite difficult. As far as I'm aware, we currently do not know if your brain is doing the same thing as mine when we hear songs in our r

I imagine that would be quite difficult. As far as I'm aware, we currently do not know if your brain is doing the same thing as mine when we hear songs in our respective heads. So first you have the problem of extracting the information. But then you have the potentially bigger problem of translating the information! We can be fairly sure that when you hear music in your head, nothing is actually vibrating in your head to produce the sound. My guess is that you have a bank of "instrument memories" and "note memories," and you can imagine new music by smashing a note memory into an instrument memory. (Similarly, try to imagine President Obama saying "My fellow Americans: even electronic brain pancake crystal elderly." It's surprisingly easy to combine your memories of his voice with your bank of known words.) But what guarantee is there that my instrument memories are the same as yours, or that they are stored in the same way? The mapping is not clear.