Four of the eight secondary keys were picked for signature generation. Record label, genre, year, and artist were used to form the signatures. Each secondary key was given a byte (in order from the list above) to disjointly set. The key was enconded and set into its byte.
The transformation made on each secondary key is similar to that which is used to generate the numeric key for the primary key. The ASCII values for the characters in the secondary key are summed together. The modulus of the result with eight gives the bit which should be set in the disjoint section of the signature for that key.
This generic transformation simplified the code, yet still produced collisions.