This discussion began with the different systems of solfège commonly used in popular songs and classical piano. It then moved into absolute pitch, relative pitch, tonal perception, transposition and register. Along the way, Geoff and Vale corrected an easy misunderstanding: when transposition changes the brightness or weight of music, the difference may not come from the name of the key itself. It may come instead from a change in register and in the physical sound that reaches the listener.