Chordplus lite allows a user to input musical chord progressions simply and then have them played back via an internal or external midi sound generator in a number of popular music styles. It is very simple and intuitive to use. The 'Lite' version is a free download for Windows.
I installed it via Crossover on a Macbook Pro running Snow Leopard. It installed effortlessly and all functions worked as advertised. The version I installed played one semitone below what was shown (which can be fixed by transposing up in the software.) That seems to an error in the original software.