Before selecting a midi IN or midi OUT device in midi mode sound in all programs modes is produced using the computer speaker. This is shown by the gray color of the speaker button background.
midi out device selected and started
As soon as a midi IN or midi OUT device is selected sound is produced using the computer midi driver on the internal computer speaker or on an external midi instrument. The background color of the speaker button changes to red.
DirectX midi
Anywhere in the program, whether on chords, table, melody or playmodes, the background color of the speaker button tells whether DirectX sound or midi sound is being produced.