There is a difference between the stop button and the stop midi button.

The stop button stops recording or playing and reverts the corresponding record or play buttons to the non-started state:

        midi OUT device started                                                     midi OUT device selected but not started

The stop midi button unselects both the midi IN and the midi OUT devices and reverts the record and play buttons to the disabled state:

Topping midi has also the effect of reverting from using midi drivers to produce sound to using the default DirectX Sound of FastChords.  See Midi and DirectX Sound.