I have an ensemble recording (contemporary classical) where the piano was not miked properly. The piano is there, but too quiet. I would like to add midi piano to the live track to increase the piano sound. I need to synch it as close as possible. I realize that there will be places where the mix will not work, but I am hoping that the effect will be an improvement. The existing recording does not have a repetitive rhythm track for easily establishing the tempo. The tempo varies frequently during each movement, so I need to establish a variety of tempi. Does anyone have some advice?