A time consuming composite

I posted this picture about 3 years ago, but I wanted to revisit it because it took so long to make it and I'm happy with the results. I photographed the models at the harp in Venice during my annual photo workshop there. I then meticulously selected the three elements -- the two women and the harp -- using the pen tool (Select > subject would never work with this kind of situation), and pasted that selection into a palace in Moscow. The real challenge, of course, was defining the strings from the background. In the end, I had 53 channels in the file -- the most I've ever had. Each string had to be selected individually, and the edges were softened ever so slightly with a one pixel feather to make the subjects meld with their new environment perfectly. I've added below a screen capture of the harp strings showing the interior of the Russian palace through them.