My Ds is 3 and half and is just now starting to talk in sentences. The only way we knew he was advanced was he would point to stuff when we asked him. Sort of a fluke thing. Anyway, he had OT, ST and DT. His speech therapist could not get over the stuff he knew. We also have a librarian that we have become close to and she has 3 GT kids and said her Dh didn't talk until he was 3 and he was GT too.
Even though he is talking now we are still having trouble understanding him. I am trying to decide if we need to take him to ST again (he aged out of the state one).
I did read the Eistein syndrome book and I don't know if it can really apply to him. We don't have any really musical people in our family and he doesn't really seem musical yet.