When you set a Track to play an Instrument, you create a link between the Track and the devices in your Setup. Please note that this is not an absolute link to a certain type of device. For example, just because a Track is linked to your definition of a Roland JD-800, this does not mean this Track will automatically access the JD-800 in any MIDI rig. In other words, you can’t just automatically move Songs between rigs, you have to make adjustments to the Setup to get things working properly.