AR Trackable for a Piano

I´m making an Augmented Reality piano, but I´m having problems getting the virtual buttons to work well.

I created the image target on the attachment. And the SDK recognized the image and the buttons perfectly (Each note´s virtual button is a penguin because I could not get it to work with just the plain white keys)

However the problem I´m getting is that when the user presses a black note o a chord it hide other notes with parts of their hands, making the app play sounds of notes it should not play.

I think this can be solved by putting the image into perspective as in the second attachment.. However, the image target is not recognized when the phone is in this position. Can I make anything to make the image targe recognized in perspective? Or is there any tool I can use to put an 2d  image into a perspective like this?

Thanks