Staying focused

So, now I have two books going and need to decide which one to concentrate on. How do you do it? First one character talks to me and right in the middle of an exciting exchange a character from the other book will butt in. If anyone has suggestions for keeping one's nose to the grindstone and ignoring all the other ideas bouncing around in your head let me know. Until then? Maybe I will write a scene where the character is tied up and gagged. This will free me up to concentrate and focus. Hmm, wonder what kind of rope I should use?