A Launch File is a file that is automatically "opened" outside of kJams whenever that song is played. For example, you may have Lyrics sheets that are text documents, that you want to be shown when you play a song. Or each song may have it's own "script" that runs, doing something unique, like set stage lighting, or play a movie in QuickTime. Each song has it's own separate launch file.
To set a launch file, select the song and go "Advanced->Special->Set Launch file", and pick your file. You can remove the launch file by "Advanced->Special->Clear Launch file".
In kJams 2, you can set a Python script to be a launch file (script must reside in kJams "Python" folder).
Launch Midi Files
kJams does not play Midi files. If you add them to the kJams Library, they will automatically open using an external player.