That is tricky to do. I have heard of people being able to EQ them out by doing a CENTER SOLO or something, which is typically where the vocals are in the mix of most songs. However, if the entire mix is mono this probably won't work. I am not sure if transcribe has this function; but honestly this is nearly impossible to do at least to my knowledge. Again, vocals and guitar solos are typically panned up the middle and if the mix is in stereo sometimes you can just solo the center to hear them; although they will not be completely soloed. Unless there is some gizmo out there I have not heard of, I would say you are going to have a tough time with this honestly.

But, I could be wrong. Good luck! :D