The TP40 has 88 keys.  I have found that you can download the circuit from the Doepfer Website. Go to the Products, Spare Parts and you will see the 88 note keybed in the first section. Click on Matrix_88.gif As I understand it the idea is that the signals T0 to T7 are "strobes" which sequentially transfer the switch status from the keys in pairs.  There are 176 switches for the 88 keys.  The 1st and 2nd switches are mechanically arranged so that the 1st contact closes first and the 2nd conta